It hardly seems possible that Michael McDonald—the longest-running cast member of FOX’s MADtv and the undeniable anchor of that show until he left last year—began his professional life as something as unfunny as a loan officer. In just under a decade, he created a bevy of characters that are as much a part of popular culture as Dana Carvey’s Church Lady: Stuart Larkin, the overgrown, sometimes partially dressed, uncontrollable, and clinically disturbed mama’s boy who has a knack for equal-opportunity offending (Apologizing to his Aunt Noreen: “I’m sorry you’re ugly”); Rusty Miller, the carrot-topped Cal State nerd who’s obsessed with his endowment (“Not just in length, but girth too”); and Marvin Tikvah, the Jewish producer and self-described “great lay.” While they might not get Stuart in all his white-faced, red-lipped glory, fans of McDonald can expect him to at least abide by his creation’s most frequent excuse: “I just can’t help myself.” MCDONALD PERFORMS AT 8 and 10:30 P.M. AT THE DC IMPROV, 1140 CONNECTICUT AVE. NW. $20. (202) 296-7008.