Guess who’s gone shagadellic: Calvert DeForest, better known as Dave Letterman’s one-time TV sidekick Larry “Bud” Melman. Calvert’s about to launch a new CD of lounge music, “Calvert DeForest’s Erotic Experience” (on the Mars label . . . and aren’t men from Mars?). Cuts include such avant-garde ’60s slices as “Music to Watch Girls By” and the “Peter Gunn” theme. Calvert also chimes in with his own version of “Tequila.” The packaging says it all: Calvert’s posed on the cover alongside a bevy of buxom Bond-girl-like beauties. Inside is a poster of him cavorting in front of the Las Vegas Sands’ marquee with Sinatra and the Rat Pack. Ring-a-ding-ding.