Namco Museum Classics Vol. 4 (PSX)

Hidden Return Of Ishtar game:
Enter the Museum and go to the Return Of Ishtar room. Then, quickly press Right, Left, Up, Down, Circle.
Now a hidden version of the Return of Ishtar game will begin.

Alternate introduction:
When the Namco logo scrolls past while the game is loading, hold L1 + R1.
Now the FMV introduction sequence from the Genji and Heiki Clan will be displayed.