1956, the pivotal year, the year after which Elvis could never turn back.
Two songs: Heartbreak Hotel and Hound Dog. Watch Heartbreak Hotel first and dig his crazy energy. Watch him get gone on that instrumental break. He's playing with his audience, but not too much--it's a pretty straight performance. Ignore the half-ass horn section added on in the background by the TV people.
Now watch another TV appearance, this time singing the Big Mama Thornton number Hound Dog. He's got the Jordanaires backing him up; their job is mostly to clap and look spiffy. This time Elvis is definitely full of himself here--watch him tease his audience, grinning and goofing, telling them "this song here's one of the saddest songs we've ever heard." Check out how he pretends to start the song, then pauses, just to crank up the screaming from the audience. I love it. This man is having fun.