Dick Is From Mars, Sally Is From Venus - S1-E4
Continuity mistake: In this episode Dick decides that Tommy has to go to school, but in 1-2 "Post Nasal Dick" Tommy already goes to school.
Suggested correction: That's just because these episodes were aired out of order of their production. "Dick Is From Mars, Sally Is From Venus" was the 2nd episode produced (production code 102) while "Post Nasal Dick" was the 5th episode produced (production code 105).