Berry Punch went to Earth for St. Patrick's Day and brought back leprechauns (always check your luggage for leprechauns). Now they're in Ponyville, and being leprechauns they're naturally looking for the pot of gold at the end of the rainbow. Well, there's only one Rainbow in Ponyville, and it's plainly obvious where the rainbow ends.

TRIGGER WARNING: the obvious place where the rainbow ends, the other obvious place, something that is probably a fetish, implied coprophagia, shipping, blatant disregard for canon, likely insulting to the Irish.