Frobisher

"My friends call me Frobisher. My enemies call
me Mr. Frobisher. And the junk mail department
of the Galactic Readers' Digest call me Mrs. F R Rubbisher — but that's neither here nor there."

While technically capable of turning into nearly
any form, Frobisher ultimately found he preferred
the shape of a small grey alien, staying in that body
for most of his life.