Oh yes, I know that show. Back in the days when I was watching FOP from Disney Channel (oh boy they had something from the opposition). So that change of animation happened on season 2? Was there a season 0 or just a season 1?
Either way, the animation may have improved with the other characters, unless we're talking about Crockpot. In Crocker's case, his head went from bulky and large to bulky but compact, his glasses changed completely (exactly like Tootie's), and he looks less scarier than he was before. Wait a second, as the generations advanced, their look now reflected their personality well! Wanda looked more wiser by time, Cosmo's dumber when you look at him, Dad and Mom became less of a couple, and Vicky is plain scarier even if you don't know her.
And Timmy's look still feels like good ol' Timmy :/ .
Well still, the above changes can't be compared to Mr. Crocker's. I feel like he's the one who has been changed to reflect his persona more than the above names. Poor Crockpot :_(