Borderlands 2 has a lot of hidden secrets, secret messages, references to popular culture, and other types of Easter Eggs.
This is the list of Easter Eggs in Borderlands 2
Contents
References to other games
Skyrim
Bullet to the Knee - A Sanctuary Citizen tells you "I used to be a Vault Hunter like you, until I took a bullet to the knee". Reference to Skyrim's famous line the guards the says, "I used to be an adventurer like you until I took an Arrow to the Knee"
Donkey Kong
Donkey Mong - A Bullymong named after the enemy from Donkey Kong, it even throws barrels at you. There is also the achievement you get for killing it, "Definitely An Italian Plumber", which is a reference to Mario.
Duke Nukem
derp Nukem - A Rocket Launcher with the Duke Nukem logo on it, causes a nuclear blast visual effect.
References to movies and comics
Batman
Rakkman - A reference to Batman. Killed his parents, lives in a The Rakk Cave, and comes complete with a Rakkarang, Smoke Bomb, and a colony of Rakks.
3:10 to Yuma
3:10 to Kaboom - This mission is a reference to the famous movie, 3:10 to Yuma. Both deal with a train.
King Kong
King Mong - A reference to the classic "King Kong" movie.
Dirty Harry
The Unkempt Harold pistol says: "Did I fire six shots, or only five? Three? Seven. Whatever.", A reference to the Dirty Harry Quote "Did he fire six shots or only five?"
Logan's Run
The Dynamic Logan's Gun pistol says: "Gun, Gunner!", A reference to the Logan's Run Quote: "Run, Runner!"
QR Codes
In Dr. Zed's Clinic QR Code - It says: "Thank you so much for playing our game, now I'm rich with love AND money! !!Nick Wilson!! Ditto!!". Nick Wilson is a Geabox Software Developer.
Other References
Heyo Steve - You find Steve in the The Holy Spirits. "Heyoo Heyooooo Heyoo Heyooooo"
Impaler: Red text says "Vlad would be proud.", a reference to Vlad the Impaler
Whiskey Tango Foxtrot: The "WTF Shield"
Fabled Tortoise: Red text says "Win by a hare", a reference to the famous fable, The Tortoise and the Hare.