With one character cameo, That '90s Show can finally resolve a lingering mystery that began in its parent series, That '70s Show. The Netflix spinoff, That '90s Show, follows Eric Forman and Donna Pinciotti's daughter, Leia Forman. So far, the series' original-show cameo roster includes Mila Kunis and Ashton Kutcher as Jackie Burkhart and Michael Kelso, respectively. Wilmer Valderrama also returns as Fez, a fan-favorite character who allows the actor to showcase his comedic genius.

While Topher Grace and Laura Prepon reprise their roles as Eric and Donna, Grace only shows up in the pilot, though Prepon makes several cameo appearances. None of the original characters are all that crucial to That '90s Show, aside from series regulars Debra Jo Rupp and Kurtwood Smith, who play Kitty and Red Forman. With a second season premiere on the horizon, another exciting That '90s Show cameo can come to pass and, hopefully, clear up Kitty's confusing family tree once and for all.

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Penny Making A Cameo In That '90s Show Can Finally Confirm If Kitty Has Another Sibling

Brittany Daniel as Penny in That 70s Show

On That '70s Show, season 4, episode 14, "Eric's Hot Cousin," Eric's cousin Penny Sigurdson comes to town. However, while Kitty's twin sister Paula also appears in the series, it's clear she doesn't have any kids. The series never addresses who Penny's parents are, only that she's somehow related to Kitty's side of the family since her last name matches Kitty's maiden name. Penny's last name suggests Kitty may have a brother. Although no such sibling is ever mentioned, he might be Penny's father — if he exists in the world of That '70s Show at all.

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If That '90s Show features a cameo from Eric's cousin, the series can finally address Penny's mysterious parentage. Not only that, but it can delve deeper into Kitty's family tree and reveal why her other sibling(s) never appear in the original show. Although the episode that features Penny is an example of a That '70s Show Kitty storyline that would never fly today, it's still exciting to consider what Penny's return on That '90s Show means for the series' shared canon.

Penny's Possible That '90s Show Return Would Create A Problem With That '70s Show's First Spinoff

That 80s Show cast

Unfortunately, Penny's return to That '90s Show also complicates the shows' shared universe. Actor Brittany Daniel also starred as Sophia in That '80s Show. The 1980s-set series isn't exactly a spinoff but a spiritual successor that's written and produced by the same team. Unlike That '90s Show, it boasts a completely new cast and never sees its storylines or characters crossover with those of That '70s Show. Since That '80s Show isn't a proper spinoff, Daniel is technically fine to return to That '90s Show as Penny without creating any in-universe plot holes.