The Secret Missing Episode of Lamput.
This is a prequel to the series, that aired on Cartoon Network on 2016.
In the laboratory, Lamput slides into a chemical storage cabinet. Fit Man tries to alert the theoretical physicist of Lamput's predicament but they're too busy to pay attention. Meanwhile, inside the chemical storage cabinet, things get messy. Lamput slides into Specs Doc and Skinny Doc, two evil scientists expelled from the director's office 2 minutes ago. Now, the scientists getting out for revenge!
This short film is found as a video on Vaibhav Studios website. Watch it, I FOUND THIS EPISODE A LONG TIME AGO: