I finally stumped him with porn.
I was thinking of Lily Thai and he thought it was Mika Tan. He finally got it after 26 questions.
I don't know if I should be satisfied or ashamed. I'm pretty sure I could stump him completely if I think of some no-name side character from an obscure movie or short lived tv show.
Edit: Finally stumped him with Vanessa Huxtable. That's not very obscure, but he guessed Rudy Huxtable, then Ashley Banks, then some little girl from My Wife and Kids.