Michael C. Hall -- 'Dexter' Star Gets New Tattoo in L.A.

"Dexter" star Michael C. Hall took a needle to the foot in Hollywood yesterday during an ink session at a Hollywood tattoo parlor ... and TMZ caught the whole thing on tape.

We spotted Hall at the True Tattoo shop in L.A. ... where an artist was working on a mysterious tat on the top of Michael's right foot.

On his way out of the parlor, we asked Hall about the design ... and he quipped back, "I'm just doctoring up my alien markings."

Check out the pic -- looks like he was telling the truth.