Factual error: The gang keeps referring to the theme park 'Great America' as "Six Flags." Up until the 80's the park was actually Marriott's Great America. There is no other Six Flags theme park in the area. - from Wikipedia "Marriott Corporation began construction on the park in 1974, and opened it in 1976 as "Marriott's Great America". In 1984, the park was purchased by Six Flags Corporation, becoming the 7th Six Flags park."
Factual error: During the episode, it goes back to 1968 and in the closing credits Eric is listed as being 7. However, he can't be because in 'Eric's Birthday' it was 1976 and he had turned 17. Thus in '68 he would have had to be 8 or 9 (depending on his birth) but certainly not 7.
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.