The milk carton guy is hard because he's just angular and straight shapes. As you can see in these milk carton drawings - I was really just trying to get shapes and gestures down - no construction.
Early sketches of the characters
The Banana guy is based off those rap artists in the early 90s with their tall cuts.
Oh yeah, me and my pal Gabe were trying to figure out how to simplify or caricature the animator Glen Keane. I think his was the most successful (if he bothers to upload it online). Here are mine done in Sharpies.