Writer:	Trey Parker
Director:	Trey Parker
Star:	Trey Parker (Voice of Stan Marsh; Eric Theodore Cartman; Herbert Garrison; Officer Barbrady; Terrance; Timmy; Ned Gerblanski; Satan; Randy Ma),  Matt Stone (Voice of Kyle Broflovski; Kenny McKormick; Gerald Broflovski; Pip Pirrup; Jesus; Jimbo Kearn; Phillip; Saddam; Various Others),  Mary Kay Bergman (Voice of Wendy Testaburger; Liane Cartman; Sheila Broflovski; Sharon Marsh; Mrs. McKormick; Mayor McDaniels; Ms. Crabtree; Princ),  Isaac Hayes (Voice of Jerome "Chef" McElroy)
Guest Star:	Genevieve Thomas Colvin (Vocals for Unknown)

The "Spooky Vision" joke used in the entire episode usually gets aired in reruns, however, due to viewer complaints, Comedy Central has extracted it from recent airings. However, the Spooky Vision effect is still viewable on the Season 2 DVD. (edit) In the scenes featuring Cartman and Evil Cartman together, a line appears down the center of the screen. The background on either side is uneven, including the mountains and even Kenny. This is a jab at the technique of film-splicing used by live-action programs that feature "twins" portrayed by the same actor; often, when this method is used, the film isn't precisely joined together, causing discrepancies in the symmetry of the image. (edit) Matt and Trey keep on saying that they don't hate the people they make fun of. Indeed they mostly like them. The great exception is Barbara Streisand, they hate her. (edit) The opening theme was changed for this Halloween episode. (edit) This episode was broadcast in "Spooky Vision," which consisted of images of Barbra Streisand located in each corner of the screen, throughout the entire episode. (edit)

(singing)
Cartman :
You guys a hella stupid,
You guys a hella lame,
You guys a hella dumb,
hella, hella, hella. (edit) Evil Cartman: No you guys, murder is never the answer. (edit) Sharon Marsh: (singing to Stan) Hush little baby, don't say a word, momma's gonna buy you a mockingbird. If that mockingbird don't sing, momma's gonna bury it in the backyard… (edit) Mr. McCormick: Kenny, wasn't that your fat, racist, foul-mouthed friend Eric Cartman?
Kenny: Mmm, Hmm. (edit) Stan: Dude, my mom's having her monthly visitor.
Kyle: Aunt Flo?
Stan: Yeah, every time she shows up - my mom turns into a total bitch! (edit)

Second and final mention of Officer Barbrady's wife. (edit) Unlike the other animals that came from the evil universe, the fish's eyes don't glow red. (edit) Visitor Sighting: When Eric's about to meet his evil twin, an alien head is seen in the picture of the bus stop sign in place of a normal head. (edit) This episode marks the first time that when Kenny dies, neither Stan or Kyle say anything about it (usually, Stan will say, "Oh my god, they killed Kenny." and Kyle will say, "You bastards!"). (edit) It is never explained why Sharon took off Officer Barbrady's pants. (edit)

Pet Sematary:

"Indian Burial Ground Pet Store" is the name of the shop, where the evil killer fish is from. In the Stephen King book Pet Sematary, there is an Indian Cemetery, and if someone buries something (for example a pet) into it, it will come back to life, but will be bad and dangerous. (edit) Poltergeist:

The "opposite" universe thing was used in many films, but when they are at the pet shop and he opens the white door and says this was built over a cemetery… that's all taken from Tobe Hooper's 1982 film Poltergeist.

In addition, the scene of Stan being afraid of his fish and looking under the bed for it and throwing something on top of the bowl because he is scared is from a scene in Poltergeist when the boy is afraid of his clown doll. Also, the part where the fish bowl keeps getting closer is reminiscent of the scene from poltergeist when the boy is afraid of the thunder and so is counting the time between thunder and lightning to see how close the thunderstorm is getting, and it keeps getting closer and closer until it is THERE. (edit) Knight Rider:

The trick about the evil twin having a goatee was also used in 2 episodes of Knight Rider with David Hasselhoff and his evil look-alike. (edit) A Charlie Brown Christmas:

Stan: I never thought it was such a bad little squash. It just needed some tender loving care.

This is a reference to the 1965 TV special, A Charlie Brown Christmas. In the special, the character of Linus speaks of a rather pathetic Christmas tree:

Linus: I never thought it was such a bad little tree. It's not bad at all, really. Maybe all it needs is a little love. (edit) Aunt Flo:

Aunt Flo is another way of saying 'a woman's period'. (edit)