It's possibly easier to post all of these 3 images together because they were initially connected, but someone commissioned for Wakko pissing and needing to fart. 
I think everyone expected that what ever Animaniacs rival was going to happen, Skippy would be an adult. Skippy would age up with the years, and be surprised that the Warners were eternal, as they are playing 'children' for the show. He was just wanting to catch up on old times.