"Dr. Grogan was once a surgeon of distinction who served in the Royal Navy. That was before he took to drinking. He got his nickname for being - as you can imagine - so full of grog that he amputated the wrong leg of an able bodied First Mate. Justice demanded he either hang from the yardarms or take his chances with the sharks and jump ship on the high sea. He took the second. On the verge of drowning, Doc Grog was rescued by the Black Pearl and given passage to Tortuga. Indebted to Captain Jack Sparrow, he's still not inclined to join his or any other pirate crew for that matter. Ya see, Doc Grog gets seasick and wants no part of pirating life."
- -From Disney Pirates Online
His office can be located by the sign he hangs out front.