Many years ago at a dinner given for James Cagney's long service to movies and theatre (he started out as a song and dance man believe it or not) he stood up to give his audience his acknowledging speech and pointed out that that in no movie he'd ever made did he say the line:
"You dirty rat."
Thus thousands of impersonators were put out of a job.
https://youtu.be/XXxZCrM04uI