The beloved Fox sitcom is riddled with plot holes, inaccuracies, and things that don't add up.
Here are the biggest examples, from Donna's forgotten sisters to too many Christmas-set episodes.
Donna Pinciotti's two sisters disappear from the plot entirely.
On season one, episode two ("Eric's Birthday") it's revealed that Donna has a sister named Valerie who's away at college.
Midge, trying to comfort Kitty over her son growing up, says, "When Valerie went off to school, I felt the same way."
A few episodes later ("Eric's Burger Job"), Donna's 14-year-old sister Tina (played by Amanda Fuller) appears when Donna's left to babysit her while their parents are away.
But Tina is never seen again and Valerie isn't mentioned either.
The show even makes fun of these loose ends and pays homage to soap operas at the end of season two, episode six ("Vanstock"), when TV announcer Rod Roddy asks in the narration: "Whatever happened to Midge's daughter, Tina?"
What seemingly happened is that Donna's siblings were written out of the plot and she was treated as Bob and Midge's only child.
Skippy peanut butter jars with modern labels appear on the show.
You can see the era-inappropriate labels when Kitty puts peanut butter on celery sticks during season one, episode nine ("Thanksgiving"), and in a later episode ("Punk Chick") when Hyde and the other guys eat out of the jar while in the basement circle.
There are too many Christmas episodes within the show’s timeline.
"That '70s Show" ran for eight seasons and has a truly bonkers timeline.
The series premiere takes place on May 17, 1976, in Point Place, Wisconsin. The final episode centers on New Year's Eve 1979, as the gang prepares for the '80s.
Throughout the show's run, there are five Christmas-centric episodes: "Best Christmas Ever" (season one), "Hyde's Christmas Rager" (season three), "An Eric Forman Christmas" (season four), "Christmas" (season six), and "Winter" (season seven).
Considering that the show's timeline spans from May 1976 to January 1980, it makes no sense that there are five Christmas episodes when only four Christmases happen during that time frame.
The World Wrestling Federation (WWF) wasn't known by that moniker in the '70s.
The professional wrestling company underwent various name changes before becoming the WWE. When it was founded in the '50s, it was known as the Capitol Wrestling Corporation (CWC). The name changed to World Wide Wrestling Federation (WWWF) in 1963, then became the World Wrestling Federation (WWF) in 1979.
During season one, episode 15 ("That Wrestling Show"), the group goes to Kenosha to see Rocky Johnson (played by guest star Dwayne "The Rock" Johnson) and other wrestlers compete.
There are various WWF signs around the venue, which are inaccurate because the episode is set in 1977, two years before the name changes.
Krispy Kreme donut boxes appear on the show, even though the popular chain didn't expand to Wisconsin until 2001.
But yet, the brand's donut boxes are seen on "That '70s Show." For example, Midge has a box on season one, episode 19 ("Prom Night") and so does Red on season two, episode 11 ("Laurie Moves Out").
Eric has Spider-Man-themed bedding that didn't exist in the '70s.
On season two, episode eight ("Sleepover"), Eric has as Spider-Man pillow and comforter.
Fans familiar with Canadian history will be bothered by the season three episode titled "Canadian Road Trip."
During the episode, the guys go on a road trip to Canada to get beers. Before reaching the border checkpoint, they hide Fez in the back with the alcohol because he misplaced his green card.
Fez gets caught by the officers and the whole group is questioned in the Canadian border office.
One of the maps on the wall features Nunavut, which didn't become a territory in Northern Canada until 1999.
Eric references "Sophie's Choice," even though the book wasn't released until 1979.
"That '70s Show" is set in 1978 during season four, episode 13 ("Jackie Says Cheese").
So when Eric cracks a joke about Jackie having to decide between money or her relationship with Kelso, his reference isn't historically accurate because William Styron's book and the 1982 movie adaptation didn't exist yet.
The gang mentions Six Flags multiple times.
During season four, episode 26 ("Everybody Loves Casey"), Jackie gives Kelso a Cosmopolitan magazine to read so they can understand why people cheat in relationships.
Later in the episode, Kelso tells Eric that the magazine taught him how complex the anatomy of the female reproductive system is.
"There's this diagram, and it's like a map of Six Flags," Kelso says.
Then at the end of the episode, Hyde, Eric, Kelso, and Fez look through Cosmo and Fez says, "Oh, look. Six Flags!"
The park comes up again on season five, episode 21 ("Trampled Under Foot"), when Donna introduces the group to a girl whose dad works for Six Flags.
The amusement park that they reference, presumably the one nearby in Illinois, opened in Gurnee in 1976 and was known as Marriott's Great America. The name changed to Six Flags Great America after it was acquired in 1984.
During a season five episode, Hyde and Jackie briefly dance to ABBA's hit song "Dancing Queen."
The issue is that "Dancing Queen" wasn't included on the group's "Greatest Hits" compilation album that Hyde and Jackie play.
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