Justin Bieber appeared on Late Night with David Letterman ... and had no problem joking about his paternity test. Mariah Yeater, who claimed Bieber fathered her son, had requested that JB take the test to prove he's the father.

Biebs and Letterman both referred to Yeater as a "weasel." He then went on to tell the host:

    "I am 17, but it is going to happen.Being in the spotlight. I took it. They just swab your mouth."

Despite the negative press this accusation brought to the 17-year-old performer, seems as though he's managed to come out on top. Perhaps girlfriend Selena Gomez has kept his spirits bright throughout all the baby mama drama.

Looks like laughter is the best medicine!