Unlockable games within games

[cha cha]

Unbeknownst to a lot of people there was an unlockable game in the arcade version of NBA Jam TE- a hidden 'tank' game that allows you to run around a 3D wireframe field. In order to access this mode however, you were required to be able to toggle the on/off switch located behind the machine. While the game was powering back on, you would hold Up + all buttons on player 1 and Down + all buttons on player 2.

I remember doing this as a kid, no one ever believed me in the latter years and I am glad it was finally allowed in the wiki entry for NBA Jam ~_^ (took me forever to get the edit allowed).

Anyone else remember it?

[Key-Glyph]

It's well-known, but LucasArts' Day of the Tentacle has its predecessor Maniac Mansion built in for play if Bernard uses the computer in Ed Edison's room. I always thought that was a cute touch.

[dunpeal2064]

Animal Crossing had quite a few

Cave's VN "Instant Brain" has Dodonpachi as an unlockable game, and it can be played with the Kinect

Zone of the Enders 2 has an unlockable Gradius game called Zoradius.

[Hobie-wan]

Don't forget the best one ever. Super Turbo Turkey Puncher.

[ExedExes]

The SNES version of Space Invaders (based off Space Invaders DX in arcade) by way of the GB port using a Super Game Boy.

[Damm64]

You can unlock xevious on Star Fox Assault for the game cube. I need to work on that.

[BoneSnapDeez]

There's a Fantasy Zone level in Arnold Palmer Tournament Golf.