A Pony Kisser is a guy who finds a "Pony" attractive. Where a "Pony" is a girl who wears a lot of makeup, does up her hair every day, wears really fancy clothes everywhere, and obnoxiously large and sparkly jewelry in order to hide the fact that underneath all of that she is just an ugly little horse.
BCH: You see that Pony Gary is making out with?
Garrett: Oh My Gad! She is nasty. He can't be fooled by all that make-up, can he?
BCH: Ha! That Goof, he's such a Pony Kisser.