A dialogue from the movie Annie Hall: (clip)
Tony Lacey: You know who the original owners were? Nelson Eddy, then Legs Diamond. Then you know who lived here?
Alvy Singer: Trigger.
Tony Lacey: Charlie Chaplin. Right before his un-American thing.
It sounds to me like Alvy is using "trigger" to mean "Who?" "Shoot." "Tell us." or words to that effect. I wonder if this is something people actually say (or said in the 70s when the film was made) or an Allenism (a Woody Allen invention)? Or is this a joke?