Easter eggs

Easter eggs is one of the speculation pages in The Binding of Isaac: Rebirth. Besides the obvious seeds - (Seed generator which doubles as a cheat code entry), there's lots more references to popular culture in the game.

Super Meat Boy

 * - Gotta lick 'em all! (Becomes Bandage Girl from Super Meat Boy).
 * - (Becomes Super Meat Boy).
 * - (Reference to the villain Dr. Fetus from Super Meat Boy).
 * - (Referencing C.H.A.D. shrinking after his defeat in Super Meat Boy).
 * - (Gives Isaac an appearance similar to Super Meat Boy).
 * Brownie
 * C.H.A.D. - (Reference to the boss C.H.A.D. from Super Meat Boy).
 * Larry Jr.
 * Larry Jr.

Gish

 * - Gives Isaac an appearance similar to that of Gish.
 * Clots - Enemies that appear to be smaller versions of Gish.
 * Gish - The protagonist of Edmund's 2004 game, Gish.
 * - A familiar based off of Gish.
 * Sisters Vis - A boss of Edmund's 2004 game, Gish.

Time Fcuk

 * - A reference to the smaller Steven from Time Fcuk.
 * - Attaches a small head to Isaac, similar to the smaller Steven from Time Fcuk.
 * Steven - The protagonist of Edmund's 2009 game, Time Fcuk.

Tri-achnid

 * Triachnid - The protagonist of Edmund's 2006 game, Tri-achnid.

Spewer

 * - The protagonist of Edmund's 2009 game, Spewer.

Gameboy

 * - Reference to Pacman and the Nintendo Gameboy.

Super Mario

 * - Extra Life (Reference to the 1up power-up)
 * - Homing bombs (Reference to the Bob-omb enemy from the Mario series)
 * - Turn into an invincible statue (The item's appearance is a reference to the Leaf power-up, the effect to the Tanooki suit power-up from Super Mario Bros. 3)
 * - It's time you learned how. (The cover looks like the NES Super Mario Bros. cartridge)
 * Liberty Cap - Touch fuzzy, get dizzy (Reference to level 1-7 in the Super Nintendo title Yoshi's Island)
 * - All stats up! (Reference to the Super Mushroom power-up)
 * - Speed + range up (Reference to the Mini Mushroom power-up)
 * - I'm a Big Boy Now (Reference to the Mega Mushroom power-up)

Pokémon

 * - (The item is a reference to Poké Balls from the Pokémon franchise.)
 * - (Reference to the infamous Missing No glitch from the first generation of Pokémon games)
 * (Reference to the mobile game Pokémon Go)
 * (Reference to a glitch in Pokemon: Red and Blue)
 * 'm (Reference to a glitch in pokemon: Red and Blue)

The Legend of Zelda

 * The general gameplay is a reference to the original NES title, right down to the hud. Coins, Keys, and Bombs are used similarly to Rupees, Keys, and Bombs in the NES game.
 * The original flash version of The Binding of Isaac uses a HUD that is a nearly direct port of the original NES Zelda title's HUD.
 * Scolex may have been inspired by Lanmola from The Legend of Zelda: A Link To The Past, both being underground and surfacing to attack before returning underground.
 * Death's Head was likely inspired by Bubbles from The Legend of Zelda on the NES, as they are both skulls that are invulnerable and maneuver by bouncing off walls.
 * Mom's Hands are a reference to Wallmasters from The Legend of Zelda.
 * Behaves like the Master Sword in 2D Zelda games

Kirby

 * Camillo Jr. - Likely a reference to Kracko Jr. from the Kirby series.

Magic: The Gathering

 * - Refers to Chaos Orb
 * - Scary
 * - Wealth... but at what cost?
 * - Extra card room
 * - Wealth... but at what cost?
 * - Extra card room

The first released four main characters you could pick in D&D are some of the playable characters in BOIR, based on the health and abilities.
 * Isaac - Fighter
 * Magdalene - Cleric
 * Cain - Thief
 * Judas - Mage
 * - Reroll your destiny
 * - Reroll Rewards!
 * - Reroll the basics
 * - REROLLLLL!

Minecraft

 * - Reference to Minecraft and its creator/former owner, Markus Persson (Known as Notch).
 * - Booom! - (Minecraft TNT).

Castlevania

 * Whore of Babylon and III - The Empress display the message "What a horrible night to have a curse." upon activation. The text comes from Castlevania II: Simon's Quest.
 * III - The Empress? shows the message "The morning sun has vanquished the horrible night.", which also comes from said game.
 * Globins may have been inspired by Red Skeletons from the Castlevania series, both having a "collapsed form" upon death before reviving itself if the form isn't killed.
 * Mask of Infamy - Carmilla from the Castlevania video game series.

Doom

 * Berserk! - The whole item is a reference to the Doomguy "Berserk" power-up. It also has "Rip and Tear" in the description, a phrase frequently used in Doom games (was first used in the 1996 Doom game when Doomguy pick up the Berserk power-up). Also, isaac can't die when this power-up is active, which is a reference to the joke of Doomguy, being "Literally too angry to die".

Other

 * - (Steam / Valve)
 * Troll Face (can be seen from Envy and Super Envy's face, Pride and Super Pride's Troll Bomb summon attack) - Internet Meme
 * - Internet meme
 * - Reusable level skip (Quote from the film Inception)
 * - Stick it to 'em (9-Inch Nails rock group)
 * Something Stinks / A Room Full Of Poop / - (Cards Against Humanity)
 * Dople - Reference to the Doppelgänger from the Tomb Raider video games.
 * (Tagline) - (Avenged Sevenfold album; Hail to the King)
 * - Reference to Mr. Meeseeks from the Rick and Morty comedy series.
 * - Reference to the Humble Bundle storefront.
 * If you go to the tainted character select screen, the taskbar icon changes to tainted Isaac instead of regular Isaac