Anachronisms: Hyde pictures Chrissy standing with two guitars (Stratocasters) strapped around her. The guitars have locking tremolos indicated by the bolts on the back of the necks. The episode takes place in '77, but locking tremolos weren't invented until around '79. The Stratocasters also have the original headstock design. During '77, Fender was owned by CBS and featured the larger "CBS design" headstock.
Continuity: In "Punk Chick" Hyde says he is leaving town with the girl. The gang is trying to get him to stay and tells him they still need to paint the water tower. They painted it in the show before "Water Tower".