Who is the only celebrity to have a "spider species" named after him?

Are you referring to Harrison Ford? (Calponia harrisonfordi species)

Make sure you don't confuse Calponia harrisonfordi with Peidole harrisonfordi, an ant found in Central America. It's a natural mistake, one that many people make.

That's it Sailracer. Good point DG. In 1993, a new species of spider -- Calponia

In 1993, a new species of spider -- Calponia
harrisonfordi -- was named after him by an arachnologist at the American Museum of Natural History to thank Ford for narrating a film. "It's a California spider, one of the most primitive members of the family Caponiidae," says a museum arachnologist. Primitive, yet brutishly handsome? "Um, it's a spider," the arachnologist replies.

It's been reported that Edward Wilson, a Harvard University scientist, has called a Central American ant, Peidole harrisonfordi . It's to honor the actor's work as vice chairman of Conservation International. - The Hawaii Channel

And now you know the rest of the story.

I believe he also named a butterfly after his daughter, Georgia. Too lazy to look up the name right now.