Michael Caine is one of my favorite actors and has a reputation for knowing lots of arcane bits of information that he brings out in conversations, ending it with what has becomes his catchphrase, “Not many people know that”.
Because of his distinctive manner of speaking he is also widely impersonated by his fellow actors. In this interview with Michael Parkinson, Caine is asked about this and impersonates himself.
The recent film The Trip starring two British comedians Rob Brydon and Steve Coogan has a hilarious bit where they compete to see who gives the better Caine impersonation (language advisory).
What is interesting is that Caine never actually said, “Not many people know that” in any film or interview before it became so strongly associated with him. The catchphrase actually originated with Peter Sellers when he did an impersonation of Caine a long time ago in an interview with the same Michael Parkinson. Not many people know that.