(Batman starts by sarcastically complimenting Sherlock's deerstalker hat, but he then tells him that it makes him look dorky. Since the hat is double-billed, it vaguely resembles a duck's head.)
I had Alfred read your books. He told me they suck.
(Alfred Pennyworth is Batman's butler. A hero like Batman doesn't have the time to read books, so he had Alfred read the Sherlock Holmes series, since he also uses his butler to do research on his opponents. Alfred comments that they weren't interesting to read.)
I'll crush your British nuts until they're bangers and mash!
(Bangers and mash—a dish consisting of sausages and mashed potatoes—is common pub fare around the British Isles from where Holmes originates, and Batman's going to make some out of Holmes' testicles.)
I've seen better detective work in Tango & Cash!
(Tango & Cash is a poorly critically-received 1989 detective movie about two detectives who are accused of a crime despite being innocent, and they try to prove themselves right. Batman states that Holmes' detective skills are worse than those shown in the movie.)
You chump! I kick punks like you off the streets,
(Batman fights villains and arrests them or takes them off the street. According to him, Holmes is just another one of these enemies who can be beaten by Batman.)
While you and Velma here are solving Scooby-Doo mysteries!
(Batman says Holmes' detective cases are weak and easy to solve, much like mysteries in the Scooby-Doo series. He also calls Watson by the name of Velma, a character in Scooby-Doo who is the smartest of the group; despite this, she is also considered to be the least liked character of the Mystery Gang. Batman also says that Watson is the smarter of the two by calling him Velma, implying that Holmes is more comparable to one of the dumber characters of Scooby-Doo.)
Nothing makes me laugh, but I bet your raps can,
(Batman is known for being serious during battle, and he is not prone to humor in any situation. However, he believes Sherlock's rhymes will be so bad, they'll actually give him something to laugh about.)
So bring it on, bitch… I'm Batman!
(Batman wants Holmes to give it his all, as he can take him on without fear. "I'm Batman" is an iconic quote first spoken in the 1989 Batman movie, and it has since then become a popular phrase associated with the character. Batman is considered to be one of the greatest comic book heroes of all time, so just the fact that he's Batman means he's capable of anything against him.)
I once met a rich fellow who smelled of guano and pain.
(Holmes uses his abilities to draw conclusions from clues to find out Batman's true identity. Gathering facts about strangers at face value simply by observing their appearance and determining the presence of certain chemicals by their smell are two common ways that he does this. He knows Batman is a wealthy person, and he detects other scents to find out more. Guano is another word for bat feces, which comes from the Batcave, Batman's secret hideout which has numerous of bats living inside. He says he reeks of bat poop, as well as pain, an emotion coming from Batman's past when his parents were murdered right in front of him, which gave him the motivation to fight against crime. Holmes says he can identify Bruce Wayne as Batman because he smells of guano and pain. This line may also allude to the Golden Anniversary issue of Detective Comics where Batman meets an aged Sherlock Holmes within the story.)
(Dr. Watson, Sherlock's partner and best friend, normally asks what Holmes says to allow the audience to know what Holmes means. Here, Watson wants clarification, as he doesn't get where Holme is going, or he's just playing along.)
I deduce this deuce stain is Bruce Wayne!
(Bruce Wayne is Batman's true identity, and Sherlock Holmes, famous for his skills of reasoning and deduction, has already figured out who Batman really is by calling him by his real name. To deduce is to arrive at a conclusion using logic, as the facts of a case are used in solving it. Deuce stain means crap, so once again, Holmes calls Batman filth.)
(Bruce Wayne is a billionaire, having inherited his deceased parents' wealth to fund his crime-fighting. Watson seems quite surprised that the rich Bruce Wayne could actually be Batman, due to Batman's efforts to conceal his secret identity.)
Yes, his wealth would allow this adversary of ours to afford the toys he needs
(Batman uses his money to buy expensive gadgets and weapons, or his "toys", to fight villains in Gotham City. Holmes says that without these supplies, Batman couldn't even be able to defend himself.)
Since he has no superpowers!
(Batman, unlike most other superheroes, has no natural powers or other supernatural enhancements. He only relies on his physical strength, intelligence, and gadgetry for fighting evil.)
You want a battle, bat? Bring it then!
(Holmes takes on Batman's challenge to fight, confident that he'll win, and he asks Batman to bring it, or use his skills against Holmes.)
I heard he has a British butler.
(Watson interrupts with a fact he wants to note that might help Holmes figure something out. He tells Holmes that Alfred Pennyworth, Bruce's butler, is British, just like them.)
Good! Then he'll be used to getting served by Englishmen!
(Holmes makes a play on words: butlers such as Alfred obey their masters by serving them. To serve someone also means they've beaten them, and since Holmes and Watson come from England like Alfred, they will serve Batman in the sense that he's being beaten, as he's already accustomed to being served by a British person.)
You're a wack vigilante black-pantied spud with no skill!
(Holmes calls Batman crazy, as well as a vigilante, someone who takes law enforcement into their own hands without legal authority. Batman was sometimes attempted to be removed by the police department and the government for being a hazard to public society. Sherlock also says Batman wears black panties, the type of underwear women use. Although he doesn't wear it in the video because the design used came from The Dark Knight trilogy, in which Batman doesn't wear them, Holmes still refers to Batman's previous design, in which he wore tights outside of his suit. A spud is a potato, and it spends most of its time underground like Batman, who only appears in the darkness and spends his time in his underground cave. Finally, Holmes insults Batman by saying he has no skill, whether it be in rapping or fighting.)
My sidekick's a doctor,
(Dr. Watson is a doctor. This also leads up to the second part of this line.)
Because his flows are so ill!
(Watson is saying that Holmes can rap better than Batman. Since Holmes' flow is "sick", he needs a doctor with him, but not to cure him, rather because ill flows show you're a great rapper.)
Shut up, nerds. I serve justice, so eat it!
(Batman thinks Holmes and Watson aren't really intelligent, and they're just nerds who need to stop talking. Heroes, like Batman, defeat the bad guys, thus "serving" justice. This is a play on words, as food can be served, and Batman is forcing them to "eat" justice. This also references the fact that Batman is a part of the Justice League.)
My sidekick only comes around…
(Batman prefers to work alone, but he sometimes requires assistance if necessary, whereas Watson is with Holmes all the time, so he says Sherlock isn't capable of doing things on his own.)
(In continuation of Batman's last line, Robin, Batman's sidekick, only helps him when the situation is out of hand, unlike Watson, who has been alongside Holmes since the start of the battle. So far, the battle has been two against one up until now, so Batman needs Robin to help even the odds.)
Boy wonder make ya wonder how your ass got killed!
(Robin is known as "The Boy Wonder", and he'll also make Holmes wonder how he had beaten them without even knowing, which could be talking about how the author of the Sherlock Holmes series had gotten tired of his character, and he was killed off at the end of the short story "The Final Problem", but the character's popularity eventually forced him to bring him back.)
Bite harder than those hounds down in Baskerville!
(The Hound of the Baskervilles is a Sherlock Holmes book involving demonic hounds with flaming jaws. Robin says he'll bite them worse than the hound.)
I'll blast you with that bat-wack-rap repellent!
(Batman and Robin in the original Batman and Robin 1966 movie have various repellents in the Batcopter; the one used in the movie was shark repellent. Here, Robin will repel Holmes and Watson's "wack" or lame raps.)
Rappel a building, snatch a villain, then by dinner be chillin'!
(Robin can scale down a building, fight a bad guy, and be finished just in time for dinner, just as fast as he can beat Sherlock Holmes and his partner.)
Got a secret 'bout your homegirl Irene Adler:
(Irene Adler is a notable female character in the Sherlock Holmes series. She was sometimes used as a romantic love interest for Holmes. Robin says there's something they should know about her, which he explains in the next line.)
Took her back to my nest to "bam pow kersplat" her!
(In the 1960s television show and comic book series for the Batman franchise, whenever there was a fight and a punch, kick, or hit landed, a comic action bubble with a sound-word would appear. "Bam", "pow" and "kersplat" are some of these words. Robin implies he took Irene Adler to his home (or "nest" as a pun on his name, Robin) and had sex with her, describing the sounds used to demonstrate it.)
I'll shatter that fiddle with a chop of the hand!
(Holmes was very talented with the violin, or fiddle, so Robin, who is a second fiddle (a character with a secondary role), will chop Holmes' violin with one swing. This could also refer to Burt Ward, the actor who played Robin in the television series, being a black belt in Taekwondo, and he impressed the producers by breaking a board with a chop.)
Holy Conan Doyle, let's get 'em! Aw, god damn!
(One of the most common running gags in the Batman series was that Batman would assess his situation, and then Robin would say, "Holy _____, Batman!", usually replacing the middle word with something related to their topic. Sir Arthur Conan Doyle is the author of the Sherlock Holmes books, so Robin says something related to Sherlock Holmes. Robin wishes to go fight, but in this line, Batman pulls out a smoke bomb and disappears from Robin's side, an action he became known for doing when he feels a conversation with someone should be ended. Robin gets upset that he was brushed aside for the rest of the battle.)
You're not smart; you're selfish! You endanger everyone's life!
(In Holmes' stories, he would, at times, use Dr. Watson and his other pals as bait to lure murderers, often putting them in danger without thinking about the effects.)
Why don't you let your boyfriend here go home to his wife?
(Holmes and Watson spend so much time together that Batman thinks they may have a gay relationship. Despite this, Dr. Watson is married to Mary Morstan, but he's around Holmes all the time. Batman says Holmes should just let his partner get away from him so he can be with his spouse.)
Nobody likes you! Not your brother, not your partner, not Scotland Yard!
(Batman says that nobody in the story likes Holmes. He has trouble getting along with other people because he always considers himself superior in intellect. His brother Mycroft has a bitter relationship with him, and Holmes even fights with Watson at times. Scotland Yard is the police station that Holmes helped during crime season, and they grew a dislike to him for his unconventional methods.)
You'll die alone with no friends except that needle in your arm!
(Batman says Holmes doesn't have any true friends, which goes back to his line saying that no one likes Holmes. Batman thinks that even Dr. Watson won't die with him. When Holmes is not solving crimes, he would take up cocaine to stimulate his mind, demonstrating that he is a drug user, which Watson disapproves. According to Batman, Sherlock will die only with the company of an intravenous drug needle in his arm.)
(In his Downey, Jr. film portrayals, Holmes' deductive-reasoning processes are given life as they project several moves ahead of his present state. That process of projection is recreated in the battle for him to plan out his last verse.)
This mustn't register on an emotional level…
(The first line from his thoughts, "This mustn't register on an emotional level," came from a boxing scene in the 2009 Sherlock Holmes movie. He begins by telling himself his emotions shouldn't mix in with his thinking, as he starts feeling loathe for Batman.)
First, exploit childhood tragedy…then gesture with pipe…
(To begin this sequence, Holmes will use Batman's tragic childhood experience against him. Afterwards, he will gesture to Watson with his trademark smoking pipe.)
(Holmes' verse will make a pun on words, so Watson will help him with completing it. Then, after Watson commends him on it, he'll accept it gladly.)
Conclude with killer catchphrase…
(He will finish the battle with his famous quote.)
(Holmes' thoughts finish here.)
I believe your parents' homicide is why you mask your face.
(Holmes begins with mentioning the murder of Bruce Wayne's parents, saying he covers his face behind a mask and fights crime in order to avenge his parents' death, but also to hide his face in shame.)
You're shamed and traumatized and haunted by the vast disgrace
(Batman is horrified of having watched his parents' deaths, and he's haunted by the memory of that night.)
Of watching like a passive waste as momma died and daddy was dispatched with haste!
(Holmes describes the brutal killing that Thomas and Martha Wayne had suffered to add effect, saying that Bruce was powerless and also calling him waste, or a piece of crap.)
Holmes, you've cracked the case!
(Watson says Holmes has figured out the source of Batman's problems. In this case, he has cracked the case, which means the mystery is solved.)
You're a batshit crazy basket case!
(Since Holmes had "cracked" the case, it means he made Batman feel unstable by bringing up the bad memories of his past. To be "batshit crazy" also means you're acting mentally insane, which also fits with Batman's bat persona. Finally, a "basket case" is a term for someone in a hopeless mental condition, so Holmes calls Batman yet another type of maniac.)
Bloody good rhymes!
("Bloody good" is a stereotypical British phrase meaning excellent. Watson compliments Sherlock by saying he had great rhymes.)
I've got tonnes!
(He's got a lot of disses. Tonnes is a different spelling of tons, usually spelled this way in the United Kingdom, like colour is to color.)
Dissing these dynamic douchebags was…elementary, my dear Watson.
(Batman and Robin are often referred to as the "Dynamic Duo", especially in the older comics, but in this verse, they're being dissed as idiotic. "Elementary, my dear Watson" is a famous line associated with Holmes, despite never having been said by him in the original books. Elementary is akin to beginner's, so here, it implies Batman and Robin could be taken down by a beginner, or an amateur.)
(Watson was impressed by how Holmes had dissed Batman and Robin, ending the rap battle with his famous quote.)