Jenny, that memorable (infamous?) Elvis performance was, I think, the same one mentioned earlier in this thread, where he was singing "Are You Lonesome Tonight?" and looked out at just the right (wrong?) moment and noticed "two bald-headed guys" sitting in the second row, which prompted the spontaneous:
"... Do you gaze at your bald head and wish you had hair?"

Whereupon he got so tickled with his impromptu pun and the audience's response that he literally broke up laughing for the remaining 2 minutes of the song.

I still can't sing that song without feeling the urge to substitute that line for "Do you gaze at your doorstep and picture me there."