I might have mentioned this before, but Butters has a poster of Orgazmo on his closet door.
Butters had a Predator experience once before...
"All you have to do is tap your heels together three times." - from The Wizard of Oz.
Kurt Russell appeared in Stargate (1994).
Last episode, Cartman dressed up as a sultan. This time, he dresses up as a king.
ManBearPig finally makes an appearance as a monster, if imaginary.
Cartman saved Kyle a few times before: in "Smug Alert" (saving him and his family during the smug storm) and in "Cherokee Hair Tampons" (by giving him a kidney - which turned out to be bad).
Kenny and Jimmy didn't appear in this episode, since Butters didn't mention them in the videotape last episode.
The Imagination Song didn't end up as a throwaway joke, as it was the key to opening the Pentagon's portal.
Kyle dying trivia: Kyle was once at risk of being written out of the show by moving away, and then by dying in season 5 (the hemorrhoid scene in "Cartmanland" comes to mind), but he recovered.
The boys have seen both Jesus and Santa in person, even gone to other parts of the world with them, but there they are in Imaginationland. On the other hand, the Woodlandn Critters, who have never been outside Cartman's imagination, now rape real soldiers there. Which begs the question: why are the good characters in Imaginationland depending on Butters to save the land when they could do it themselves?
Strawberry Shortcake is wearing cherry prints, so she should really be called Cherry Shortcake. :)
Kyle's coat is torn and blood-splattered when ManBearPig lets him go, but there's no damage to his body.