Here are the easter eggs that we know to be improved or added in the PS2 version of Escape From Monkey Island. Have fun!
Murrayball, the first pong-like game to involve bananas and a skull, is a bit improved on the PS2 version. Namely, you can now play two player Murray ball! To access it, you must look up Ryan Danz's or Rich Sun's uber-names in the Palace of Prosthesis file system controls. In case you didn't know, Danz and Sun were programmers on EMI. Once you look up either of their names, an option for Murrayball will appear under the Bonus Menu.
Monkey Invaders, a clever parody of Space Invaders (unless you're an angry lawyer from Activision... in which case, this isn't the easter egg you're looking for. Move along.) To access this game, you must completely fill in the Monkey Kombat move hint chart, which can be viewed during Monkey Kombat by hitting one of the top controller buttons. After you do this, Monkey Invaders will be available under the Bonus Menu.
There is one additional easter egg that I have not verified yet... in fact, I don't even know what it does! During the main menu, if you press up, up, down, down, left, right, left, right, square, circle, and then start, something is suppose to happen. Let me know if you get this one to work.
Many thanks to LucasArts for helping us out with these easter eggs!