Chad and Brett's biceps are at the point where they don't even need to flex. This is simply their natural shape and size now. Chad and Brett just put their forearms up to make it appear as they're flexxing . . . but this sentence defeats the purpose of that, because now everyone knows that they're not flexxing anyhow. Their posing careers are over!

No, Niles doesn't have to go to the bathroom really bad, he's just showing a
nice chest and arm flex. He claims to get all his muscle from eating raw eggs.
And when he says "eating raw eggs", he means "eating lots and lots of raw eggs."

Niles likes eggs so much because they resemble the shape and figure of his ideal woman.