Evidence A: Miss Piggy is a villain! 
Lunchbox Panel Placement

The violent and frequently jealous narcissist is featured on what I propose is the “villain” side panel of my vintage ‘The Muppets’ lunchbox:

You’ll note that for Thermos’ lunchbox ‘Indiana Jones and the Temple of Doom,’ this panel is occupied by the impressively terrifying gentleman who digs into a living man’s chest with his bare hand and tears out a beating human heart in a sacrificial ritual for Kali Ma. 

(NB: If she knew about religious rites of this kind, Miss Piggy would almost certainly demand an even more theatrical form of worship.)