Stopthisnonsenseimmediately!

While he wasn't the most competent nor coherent Power-Puff Girl foe, he was certainly the most consistent in appearances in the show, and during it's run grew into the most popular by being the funniest.

Having a soft spot for animals and melodramatically mad scientists, the grumpy Pan troglodyte is one of my favorite villains for being both.
And while he never asked for it and often exploited given sympathy, it's just like bubbles said,

"But I knew that deep down inside he was a sad, poor little monkey."

Mojo jojo© Craig McCracken and Cartoon Network