Part-Time Friends / Bio Square - S2-E19
Corrected entry: Towards the end of "Bio Square," Arnold and Helga manage to escape drowning in the titular Square (from a haywire sink leak) by jumping onto her inflatable mattress. The two ants from an experiment by Arnold manage to escape, too, by jumping off a table and onto a floating, half-eaten potato. However, at the end of the episode, when Arnold and Helga are describing their adventure before their science class, Arnold says that the ants "climbed onto the leaf." Knowing how sharp Arnold is, it's unlikely that he mistook the potato for a leaf. This is a simple script error.
Correction: Sharpness aside, Arnold is prone to making errors or mistakes. The two were about to drown and the seriousness of the situation might have mistaken him. Also at that point I don't believe there was anything to prove if he even knew the ants made it to safety so he might have believed they climbed onto a leaf. In any circumstance its at best a character mistake.
Lummie ★