Given the extensive and dramatic nature of Mr. Olsen's transformations, I'd be more inclined to say that he's a Durlan hiding out in Metropolis than a Gallifreyan. No Time Lord ever regenerated into a giant turtle man.

Ebony the Black Dragon

No documented Time Lord, that is. Who knows what happens during Prank Week at the Academy?

"Life is like an anole. Sometimes it's green. Sometimes it's brown. But it's always a small Caribbean lizard."