I get the joke - from scrawny to buff and pouting when teased.
It's funny. Sometimes I think there are those on Newgrounds who have a one-joke-track mind.
The art looks great. Your shading and lighting is spot on. You also do a nice job with facial expressions. They're exaggerated, but not overly so - plus, they depict the character feelings perfectly.
Once more, fantastic job. Glad I jumped over from your flash submission to check them out.
I was going to give you 4.5 because the style of clouds in the second and third panel seem to distract - they're more realistic than the rest - behind the characters, but then I figure that's just my personal taste.