How often does this happen today? Virtually never.
The film
The Graduate debuted December 21, 1967. A month later, Dustin Hoffmann found himself playing
The Match Game opposite Liza Minnelli.
We never see that happen nowadays. (Heck, it almost never happened then -
a quick glance at the 1968 celebrity list shows a distinct lack of major film stars (although I do note Lauren Bacall seemed to appear quite a lot).