In the level "I'm Ready, Depression...", attacking the organ will cause it to start playing music.
Contributed by Anex
If the player goes into a secret area in the level "Welcome to Planktopolis... Minions", they can see Heavy Irons timed records for the slide and racing levels.

Heavy Iron Studios were the development team for the game.
Contributed by frankfrost2
Patrick's model has "Goofy Goober" underwear, but it's always hidden under his shorts. It's possible to see it via bugs and glitches.
Contributed by xianc78