You're wrong.
One of my first contemporary memories of Niven was as the suave, debonair crook in
The Pink Panther. Much of that movie was over my head at the time. The main thing I remembered, and giggled about when re-telling it, was the recurring sight/sound of Peter Sellers being driven away in police paddy wagons, once with balloons sticking out the back doors.
I'm positive he played a sinister husband...but it's not coming to me.
He wrote some excellent, highly entertaining books, which I still have.
But I think his spontaneous quip at the Oscars--when a streaker ran across the stage--was the highlight of his wit.