Not the Number One guy (I'm pretty sure that is Dee Bradley Baker), but definitely a very good one -- he grew up in a small town in Iowa (or possibly another one of the vowel states) and used to entertain himself on his way home from school by picking a field or backyard that had animals wandering around within earshot, and then practicing their sounds until he hit the one that made everyone on the other side of the fence stop grazing or pecking, lift their heads and look around to see who was missing. And his greatest moment of triumph came the day he did a lost, hungry calf so well that a whole field of usually placid dairy cows looked up anxiously at once.
He was also really good at ineffectual grownups (he claimed that he and his wife could afford a kid and a house pretty much solely on the basis of his ability to yell, "Hey, you kids, you keep out of there!" and then sound like he'd just fallen in a hole or walked into a closed door or taken a frying pan to the head), and had a technique he called The Oscar Winning Drippy Nose.
But his panting dog was genius, it's true.