What's-his-name

Watching Dancing with the Stars' Disney night.
Donny Osmond says he was in Mulan, as the voice of Shang.

me: Donny Osmond? No way! I have to look this up. (goes to IMDB)
Huh. Who knew! He was the singing voice of Shang. But BD Wong was the real voice, you know what I mean?
Big Frog: Like what's-his name and what's-his name in The Student Prince.
me: Yeah! Oh, I was gonna say Singing in the Rain.
Big Frog (laughing): It's funny how they both have the same name, what's-his-name.
me (also laughing): And you wouldn't expect them to be in both The Student Prince and Singing in the Rain!