In fact, pretty much any reference to an episode that was aired at the time the game was released.
In Rock Bottom, standing near the vending machine at the start will cause a cutscene to start where a bus drives up, idles for a moment, then drives right off, a clever and possible to miss reference to the episode "Rock Bottom".
Five words: Retirement Home Girls Gone Wild.
In the dream world, there was a level intended for Patrick that would've been dessert-themed. However, for reasons that aren't clear, it was cut. The developers, seeing a prime chance to make another reference to the show, just make Patrick's dream a pitch black room with him standing under a spotlight where he just gives you the golden spatula you would've had to work for without any strings attached. Though considering How hard the platform is to reach it in the first place, it was probably justified.