There are several mentions of Bandstand throughout the flashback segments of this episode. Trouble is, it was all supposed to be happening in 1953. American Bandstand didn't premiere until 1957.
Bandstand premiered locally in late September 1952 as Bandstand on Philadelphia television station WFIL-TV Channel 6 (now WPVI-TV) and ABC picked it up in under the name American Bandstand, it premiered August 5, 1957.
So its not a goof :)