In each episode of the "Imaginationland" trilogy, Cartman appears dressed as a figure of authority. In this episode he is dressed as a King.

"Imaginationland: Episode II" drew over 3.6 million total viewers and was the most watched program in all of television for Wednesday night among men aged 18 to 24.

Kurt Russel: They're raping me.. they're raping all of us! It hurts.. they're raping us and it hurts!

Army General: Ever since the Cold War the U.S. Government has been working on a secret project to build a doorway into the imagination. It is called Project Imagination Doorway.
Stan: Thats not very imaginative..

Butters: Please sir, I have to get home to my world.
Imaginationland Mayor: Oh.. well.. all you have to do is tap your heels together three times.
Butters: Really?
Imaginationland Mayor: No you fucking dipshit, that was a joke!

(Cartman wakes from a dream)
Cartman: Ah AAAH!
Old Lady: You okay, kid?
Cartman: No. I've got dry balls.

Stargate:

There are several references to the film Stargate (1994). The music is clearly in reference to the film while Kurt Russell, who acted as Col. Jonathan "Jack" O'Neil in the film, is called upon to enter the Imaginationland portal. This portal looks strikingly similar to the Stargate that appears in the film.

Visual: Evil Imaginationland Characters

Jason Voorhees from the Friday the 13th films
Freddy Krueger from the A Nightmare on Elm Street films
Pinhead from the Hellraiser films
The Joker from the Batman comics
Green Goblin from the Spider-Man comics
Frakenstein's monster (appearing as the common depiction from the 1931 film adaptation)
A predator from the films of the same name
A xenomorph from the Alien films
Darth Maul from Star Wars Episode I: The Phantom Menace
A tripod machine from Steven Spielberg's War of the Worlds
Imperial Stormtroopers from Star Wars
Cylons from the original Battlestar Galactica
A T-800 model from the Terminator films
Minotaur, Medusa, and a Cyclops from Greek mythology
Khan from Star Trek II: The Wrath of Khan
Sagat and Akuma from the Street Fighter video games
Fu Manchu
Mordred from the film Excalibur
The Headless Horseman
The Creature from the Black Lagoon
Goro from the Mortal Kombat video game series
Wario from the Super Mario Brothers Nintendo video games (although he has a "V" on his hat rather than a "W")

Cartman: Previously on Battlestar Galatica..

Although the text says "Previously on South Park," Cartman actually says "Previously on Battlestar Galactica." This is a reference specific to the re-imagined series, which not only has a "previously on..." recap, but the text is also in the same style as that of Battlestar Galactica.

Cartman's attempt to resuscitate Kyle, including his slapping & outcry of “You never backed away from anything in your life! Now fight!” is an allusion to the 1989 movie ‘The Abyss’.
The character Virgil does the same thing while trying to save Lindsey.

Visual: Woodland Critters

The Woodland Critters make an appearance in this episode as part of the evil side of Imaginationland. They first appeared in "Woodland Critter Christmas," the season 8 finale episode.

Visual: Manbearpig

One of the creatures from the evil side of Imaginationland is a Manbearpig. Al Gore came to South Park in "Manbearpig" to warn everyone about this dangerous creature.