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ATLANTA -- Justin Bieberbecame a legal adult Thursday.

The teen hearthrob's fans celebrated with tidings of "Happy National Bieber Day,"a trendingTwitter topicinmetro Atlanta. That was followed closely by tweets of "Justin is OFFICIALLY 18."

Bieber, who calls Atlanta a second home,tweeted back: "dear cougars. i see the jokes. im legal. hahaha."

The pop star hada special messagefor his biggest fan: "dont worry mom im never gonna not be your boy. Love u very much. thank u."

On Ellen today, Ellen DeGeneres and Bieber's manager surprise the pop star with a new car, a Fisker Karma. Ellen airs on 11Alive at 4 p.m.

Bieberthanked his otherfansand encouraged him to celebrate his 18th birthday bydonating $18 tocharity.