We’re three songs into Ham Sandwich’s set in Whelan’s, and the entire crowd is already covered in confetti and there are maybe ten beach ball-sized balloons being batted between audience and band. Everyone in the venue is either grinning madly or openly laughing. Ham Sandwich are clearly here to have some fun. But wait: like a bunch of drunks in charge of a time machine, we’re getting ahead of ourselves. (That’s an old Mr. Biffo…