Doug Takes a Hike / Doug Rocks - S1-E4
Continuity mistake: When Roger is dancing in Skeeter's yard, he changes color.
Bug Off/The Crawl Space - S9-E5
Continuity mistake: In Moving Away, Tommy tells the other Rugrats how they first met when Angelica lied about the nasty things they did. However in the Crawl Space, there is a flashback of Tommy, Chuckie, Phil and Lil playing in the playpen when they were younger. Chuckie is scared of the Jack-in-a-box in that flashback, so the Rugrats could not have met for the first time back then.
Continuity mistake: When Marshall first finds Trip's letter, he holds it from the left side. In the close-up, he's holding it from the right side. (00:02:10)