You wouldn't know it from GTA IV's gritty, post-soviet realism, but there used to be a time when this franchise was wacky and light-hearted. A time when you wielded jetpacks, fighter planes and weaponized dildos against increasingly cartoonish odds. This egg is from that era, and it's so out there that it looks like James Franco and Joaquin Phoenix made it up at one of their metafictional postmodern orgies. If you fly your jetpack to the very top of the Gant Bridge, you'll find a large inscription reading: "There are no Easter eggs up here. Go away." Which is itself an Easter egg. But it's not. But it is. But it's - man, I wish it were still cool to make Inception jokes.
In Jolly Roger's Tavern, Banjo and Kazooie can find an old drunk pirate, rambling on about God-knows-what. A little sleuthing reveals that this drunkard, named Captain Blackeye, used to be the main villain in the original version of Banjo Kazooie, back when it was an SNES game called Project Dream. By the time it was released, however, the game's whole story had shifted: the protagonist was now a zany Bear/Bird duo, their antagonist was an evil witch, and Captain Blackeye was left on the cutting room floor. The only sensible option left for the character was to go get hammered. Now if you'll excuse me, I just played Banjo Kazooie: Nuts & Bolts and I think I'm gonna go join him.
Valve loves dropping subtle hints that all of their games take place in the same world, but no Valve-verse crossover is more fun than Gnome Chompski. An adorable garden gnome named after equally-adorable MIT linguist Noam Chomsky, this statuette appears in both Half Life 2: Episode 2 and Left 4 Dead 2. At first glance, the diminutive Mr. Chompski is just a spectacularly crappy melee weapon, but carrying him all the way through to the end nets you an achievement in each game for rescuing him (and in HL2:E2, for shooting him into space).