(TMZ) -- The guy who plays one of the troubled Gallagher kids on "Shameless" ran into some real life trouble off set -- 'cause "Carl" got busted for a DUI ... TMZ has learned.
18-year-old actor Ethan Cutkosky -- who plays William Macy's second youngest child on the show -- was arrested and booked for DUI Thursday in the L.A. area.
Law enforcement sources tell TMZ, Ethan was driving his orange BMW at around 10:30 PM and began to straddle the traffic lanes, which prompted cops to pull him over. TMZ was told he did poorly on field sobriety tests and was arrested on the spot.
It's unclear if the DUI was drug or alcohol related.
TMZ reached out to Ethan's rep ... they had no comment.
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