Justin Bieber -- Best Babysitting Gig Ever

An 18-year-old looking after a 3-year-old is pretty ordinary, but when that 18-year-old is Justin Bieber and the kid you're watching is the son of L.A. Clippers star Chris Paul ... AND you do it courtside at Staples Center ... it's just awesome.

Bieber had a front row seat last night as little Chris Paul II watched his daddy and the Clips dismantle the Boston Celtics, 106-77 -- which propels the team's winning streak to 15.