Continuity mistake: Jackie enters the basement and say: "Oh my God Donna, great story." while she is holding the newspaper by the sides. In the next shot, while the gang is laughing, she is now holding it by the bottom.
Continuity mistake: Hyde must have gone into the future to get his Spiderman pillowcase because it has the Spiderman logo from the 1990's on it, not the 1970's one.
Continuity mistake: When Kitty asks Red for a cat Red is reading a copy of Time magazine. He closes the magazine and puts it down on his knee while he tells her why he doesn't want a cat in the house but in the next shot the magazine is back in his hands and open to where it was before he closed it.
Continuity mistake: The unibrow drawn on Jackie changes between the time we first and last see it. It's thicker the second time.
Chosen answer: He isn't. Time moves slowly in the show because they didn't want it to turn into "That '80's Show". In the first episode, he say's he's 17 but the second episode was his 17th birthday so he must have been 16. The first 12 episodes are set in 1976, the next 2 seasons are set in 1977, the next 3 seasons are set in 1978, and the remaining shows take place in 1979 with the final show on Dec 31, 1979 when Eric must be 20 as he turned 17 in 1976.
Myridon