Justin Bieber: Take Your Grandpa to Work Day!

Justin Bieber may have started a new holiday by pulling a late night recording session with his grandfather!

Biebs hit up a studio in Santa Monica on Wednesday with grandpa in tow. Justin's done stuff with gramps on social media, but this is the first time we've seen them hang together at work.

Here's a couple of the dynamic duo's greatest hits ... so far.