Homer vs. the 18th Amendment - S8-E18
Continuity mistake: When Homer and Bart are escaping from the cops after stealing kegs of beer from the dump, they drive through a cemetery and slam into a headstone, breaking the right headlight of the car. When they pull into the driveway back at Evergreen Terrace, the left headlight is the broken one.
Homer vs. the 18th Amendment - S8-E18
Continuity mistake: Carl and Lenny are seen at both Moe's and at the St. Patrick's Day parade, which are happening simultaneously.