The question was posed in another thread as to the "real" story of how his trumpet first became bent. In that thread I stated I had heard it first occurred as an accident. Well, I now find that such is corroborated by what we read on his "official" website:
"And just how did Gillespie end up with that bizarre, trademark trumpet of his? The bent-bell trumpet got its start in 1953 when someone fell on his trumpet stand backstage; Gillespie liked the sound of the altered instrument so much that his trumpets were specially made from then on."