I remember watching the old Our Gang comedies, and I’ve always wondered about the boy they called Froggy.
He always spoke with a very raspy voice. Was this the result of a birth defect or an injury or was it just a trick he could do with his voice??
Here’s the IMDB biography page for “Froggy” Laughlin.
Unfortunately, that doesn’t really answer your question, but I thought looking there would at least be a start. The boy was hit and killed by a truck at the age of 16. 
My son and I both have no problem talking like Froggy. My son (born on Oct. 31st) did it in class at school one day and scared the teacher so bad she ran out of the room.
Froggy apparently inherited his unique voice from his mother, as evidenced in Robot Wrecks (1941), in which his mother is heard to have a very deep voice–courtesy of dubbing by 5’ 2" Billy Bletcher, who also played the role of Froggy’s father in that same short, and supplied the voice of the giant in Mama’s Little Pirate (1934).