My 5yo son is a S.I.T. - Superhero In Training.  There isn't anything Superhero-ey that he doesn't love.  These are no exceptions.  The only thing I would caution, he is rather tall for his age but the shirt seems rather short to me.  It fits him fine right now, but I ordered an 8 and he's only 5 and I would say we'll probably get about 6mos out of them.  Underwear does not appear to be short at all.

Good price, nice quality.  Happy S.I.T., happy Mom.