Frankie Muniz Whips Out the Big Guns

MALCOM IN THE MIDDLE… ALL GROWN UP

Frankie Muniz shows off the big guns, flexing his biceps for paparazzi after a work-out in Los Angeles on Thursday.

After working up a sweat, the pint-size actor hopped into his mustard yellow vintage Chevrolet Cheville and rode off solo.

Frankie celebrated his 22nd birthday yesterday. HAPPY BIRTHDAY, FRANKIE!