I love the internet! Guess what I found on YouTube: Bobby Darin performances! Here're some of the best ones I've found so far:
"Mack the Knife" -- It's 1959, this song has hit #1, and Bobby is 23 and cute as a baby puppy. When he does the bit about "MacHeath spends just like a sailor" I can't help but giggle like a giddy schoolgirl. Also, he's either an amazing lip-syncher already, or he's singing it live. I think it's live, because it's not the official recording version -- he throws in different little asides.
"Can't Take My Eyes Off You" -- Bobby's in his late 30's and on top of his game.
"Dream Lover" -- Also 1959. He's trying to be serious and earnest, but he keeps cracking up and smirking :-D
"Got My Mojo Workin'" -- Bobby plays both the harmonica and the vibraphone on this one! I'd never heard him sing this song, it's not on any of the cds or LPs I have, so that makes me dig it even more :-)
"Beyond the Sea" -- The joke about Tommy Sands is silly, but him slapping his own wrist is just funny. And then he segues off into bits of other random songs, which gets very fun. Just let it keep on playing, because he ends up imitating a trombone, telling odd jokes, and you get to see why he really was a consummate live entertainer.