Alfred Hitchcock always made sure that he was appearing once in each of his movies. Probably first because it reduced slightly costs, then for the sheer fun of it.
You certainly knew that the great movie director, Alfred Hitchcock, was used to, first in order to reduce budgets, then merely for fun, keep one little cameo appearance in each of his movies, sometimes even a small role. An Internet user collected them all (nearly) in a single sequence. YouTube link