According to Dunkademics, Jonathan Clark is a former UCLA track star training for the triple jump in the Olympics.  I don't know how good he is at the triple jump but from these two videos I can say his jumping ability is pretty impressive.

In one of the vids he does his best Gerald Green inspecting the rim impersonation and in the other he performs an impressive back flip before catching an alley-oop.  I would love to see Jamal Crawford and Blake Griffin attempt that.