Billy Dee Williams, known for playing Lando Calrissian in the original Star Wars Trilogy, guest starred in an episode as a preacher offering marriage advice to Donna and Eric. His character is just as obsessed with Star Wars as Eric.
Dwayne Johnson was cast as his father, Rocky Johnson, in a wrestling-themed episode. His last line, to Red, was that one day he hopes his son will become "the most electrifying man in sports entertainment." Red answers, "Yeah, good luck with that."
"It's a Wonderful Life" featured Donna hooking up with Hyde instead of Eric. In real life their actors Laura Prepon and Danny Masterson were dating.
Partially. The teenagers were about sixteen/seventeen at the beginning (with Michael a year older and Jackie a year younger): Mila Kunis (Jackie) was fourteen when the show started, Laura Prepon (Donna) was seventeen, and Wilmer Valderrama (Fez) was eighteen. The rest of the gang was played by actors aged twenty and over. Eventually, they all became examples, since they aged normally over the eight years, while their characters only aged two years.
Katey Sagal (the voice of Leela and the actress best known as Peg Bundy) plays Hyde's mother as well, making it the second time Sagal has played a selfish, negligent mother on a FOX sitcom.
That recurring character later in the series played by Jim Gaffigan.
In "Bye-Bye Basement" Leo's cousin is Richard Karn who played Al Borland.
Officer Kennedy is James Avery (a.k.a Uncle Phil).
Randy is Josh Meyers, a former cast member from MADtv (known for being paired with Ike Barinholtz in sketches and his celebrity impressions of Anna Nicole Smith's son, Daniel, Owen Wilson, Eminem, and Johnny Depp as Captain Jack Sparrow) and younger brother of Weekend Update anchorSeth Meyers (and even though they're born three years apart, they look as if they could be twinsnote the only thing that distinguishes Seth from Josh is Josh's long, reddish-brown hair, so for any viewer who sees a final season That 70s Show episode and thinks Seth Meyers was on this show, it's not him).
Laurie was portrayed by Lisa Robin Kelly until Season 6, where she was replaced by Christina Moore.
Jackie's mom was played by Eve Plumb for a brief appearance in Season 1. She returned as a recurring character in Season 6, played by Brooke Shields.
Narrowly averted with Eric when Topher Grace left after Season 7. Originally, the producers wanted Josh Meyers to play Eric in Season 8, but they instead wrote Eric off as spending a semester in Africa, and cast Meyers as a guy named Randy who became the gang's newest member. Either way, audiences didn't like the arrangement, and Randy was barely in the series finale.
Throw It In: In "The Best Christmas Ever," Kelso hops over the couch but slips and crashes his legs against the table. This was a real accident on Ashton Kutcher's part, but it was left in because it felt in-character for Kelso.
Trope Namer: That '70s Show has named That Nostalgia Show, a type of work which focuses on a specific era, not as an attempt to portray it accurately, but to play to the nostalgia of the audience, whether they have experienced the era first-hand or not.