Happy birthday, Bob Newhart! What a marvelous coincidence that his 84th birthday falls on the same night CBS is repeating his terrific Emmy-nominated guest performance on The Big Bang Theory (Thursday, 8/7c). And wouldn't it be splendid if this finally earns him an Emmy? It's unfathomable that he has yet to receive one for his illustrious career. Newhart's timing is impeccable as ever as "Professor Proton," the former TV host of a kiddie science show that Sheldon and Leonard still obsess over (so what else is new). And while they gush over meeting their hero, he's understandably much more impressed by Penny — although what she's doing with these geeky goofballs is a puzzle he'll never understand. The good news is that he's expected to return at least a few times during the next season, so maybe he'll eventually figure it out. Whatever the excuse, it's a treat to see Newhart working his magic before a live audience on one of TV's most deserving smash hits.