Always an Actor

You work as a dustman or in a shoe shop for a while, you move on and everyone forgets about it. Do work as an actor in a single role, however, and everyone refers to you as "an actor" for ever afterward.

More broadly, this is when a character has had his fifteen minutes of fame and graciously accepted its end to go back to a quiet private life—only to find that the world (or some segment of it) is not willing to let him go. This can be played as anything from simple Backstory to the lynchpin on which an entire Story Arc—be it comedic or dramatic—can be hung.

This is a supertrope to Former Child Star. Compare with White Dwarf Starlet (who wants to act again but can't land a role) and I Am Not Spock (who never stopped acting, but is only remembered for that one famous role).

Film

 * The banjo-playing boy in Deliverance is so described in "the other wiki".
 * Galaxy Quest is very largely composed of variations of, lampshades hung on, and aversions of this trope.
 * Sunset Boulevard is a tragic variation, making it at least Older Than Radio.
 * This is a plot point in The Wrestler, both with Randy (Mickey Rourke) being hassled by a fan at his butcher job, and his former in-ring nemesis The Ayatollah owning a few car dealerships.

Live-Action TV

 * The various nonentities and Z-listers who attempt to cross over from Big Brother and related shows.
 * Ann Marie in That Girl, far too obviously.