In this Halloween episode, Kitty is handing out raisins to trick-or-treaters. One trick-or-treater's mask goes from being over his face to above his head.
The gang sees "The Texas Chainsaw Massacre" in a theater. Both Hyde and Fez imply a girl dies because she was either having sex or about to have sex. There is no sexual content in that movie. Also, the audio implies she is killed by a chainsaw. The female character that dies is actually not killed by a chainsaw. In fact, despite the title of the film, only one character is killed by a chainsaw and it's the character in a wheelchair.
When the gang is burying their permanent records, the moon is shown to be a full moon during a lunar eclipse. Neither happened on Oct 31, 1977.
Kelso was held back because he couldn't, or wouldn't, learn cursive writing in kindergarten. Cursive writing isn't taught in kindergarten.
Mila Kunis (Jackie) breaks character and almost smiles after her scream.
When Kitty is handing out boxes of raisins, the boy in the tiger costume doesn't get a 'treat'.
When the gang finds their school records, they discover that Michael Kelso is one year older than Fez, Donna, Eric and Hyde. Hyde says, "You mean you are 18? You could have bought us beer!" If they are 17 or 18, they would most likely be Seniors. However, they graduate 4 years and 5 months later, in "Celebration Day" (s5e25).
Jackie says she doesn't like Texans. However, her lifelong dream is to be a Dallas Cowboys Cheerleader.
The gang finds their permanent records at the burned out elementary school. They discover that Jackie's middle name is "Beulah". In "Battle Of The Sexists" (s1e4), she wears a sweater with her initials, "JSB", on the front.
Fez is completely unaware of the rituals of Halloween although he's been in the country since well before October of the previous year.