When was the first video game easter egg?

The earliest easter egg I was able to dig up was a game I used to play on the Atari-2600 called Adventure (1978). A secret dot allowed access to a secret room.

Anyone got this beat?

Everything that I've seen supports Adventure as being the first easter egg.

Warren Robinette actually had to sneak the code out without telling anyone, because he thought he'd be forced to remove it.

The first one I remember was in Smurf: Rescue from Gargamel's Castle for Colecovision. I can't honestly remember the exact specifics, but if you happened to jump a certain way from the base of the floor, up onto the Skull, up to the platform to rescue Smurfette, her dress would slowly begin to disappear as if she is doing a striptease. :)

I too, have heard that Adventure was the first easter egg.

I hadn't heard this but since 3 of you say it I guess I will believe it.:)

Yes!!! I loved that game!! Maybe her dress disappeared because of the farting noises you made as you jumped up there. :)