This article is from the alt.fan.harrison-ford FAQ, by Angela Boyko neptunia@geocities.com with numerous contributions by others.
No. I don't know where this idea came from, but some sources falsely
claim that Harrison appeared in a 1957 episode as Chester Anderson. David
Letterman went so far as to show a clip of the show to Harrison during
one of his appearances on Letterman's show. The boy doesn't look anything
like Harrison, who was 15 years old in 1957, long before he ever acted.
Harrison seemed amused by the idea, but denied that he ever appeared on
that TV show.
 
Continue to: