I don't know what kind of depo prep he went through, but I generally include a portion I call "don't be an *sshole" (except I frame it professionally and courteously of course). The gist of it should be pretty obvious: the deposition "counts" as testimony and anything you say may find its way in front of a judge and a jury so don't come off as a jerk.
In Justin Bieber's case: Mission NOT-Accomplished.
Here's one clip (embedded - email subscribers should just click the link above to view online).
Closest thing I could find to an employment law tie-in:
ATTORNEY: Have you ever disciplined [name]?
BIEBS: Disciplined? What kind of question is that? Is he my son?
No Biebs, sometimes you have a duty to supervise your agents, employees, etc.