Robin

Robin backed up Batman in Epic Rap Battles of History 26 and was played by Lloyd Ahlquist.

Information on the rapper
Robin 'The Boy Wonder' is a DC superhero mostly known as Batman's sidekick and counterpart. He gained lots of popularity, resulting in him also getting solo adventures. The team of Batman and Robin is commonly refered to as The Dynamic Duo. Characters who took the identity of Robin include Dick Grayson, Jason Todd, Stephanie Brown, Damian Wayne and Tim Drake. Robin also is a main character in the TV series 'Teen Titans'. The Robin in ERB seems to be Dick Grayson. Robin later becomes Nightwing when he leaves his partnership with Batman.

Verse 1:
...When he's needed!

Boy wonder make ya wonder how your ass got killed

Bite harder than those hounds down in Baskerville

I'll bust you with that bat-wack-rap repellant

Rappel a building, snatch a villain, and by dinner be chillin'

Got a secret 'bout your homegirl, Irene Adler

Took her back to my nest to bam pow kersplat her

I'll shatter that fiddle with a chop of them hand!

Holy Conan Doyle, let's get 'em! Aw god damn!

Trivia

 * Batman and Robin are the first superheroes to appear in an ERB.