I didn't even realize the bit about Cappy's eyes when he laughs. Man, I love those little touches Nintendo throws into their games.
I'm really curious to see if Cappy will become a mainstay in the Mario series moving forward.
On one hand, he lends so much to improving manuverability in 3D Mario games. And he's pretty inconspicuous when just sitting on Mario's head.
On the other hand, they'd have to keep creating plots/mechanics around his capture ability. Attempting to lampshade it would be kind of awkward considering that's a major factor of his.