Watch: Lisa Kudrow explains why it's so difficult to find Conan O'Brien's Irish ancestry

Lisa Kudrow may know who she is and who a lot of the celebs on 'Who Do You Think You Are?' are, but Conan O'Brien? That's another story.

Kudrow is the executive producer of the show's US format, and while on Conan last night, he tackled her with a question as to why it was taking so long for the show to get to the roots of O'Brien's ancestry.

The answer? An obvious roadblock that is as plain as the nose on Conan's Celtic face.

We have to say though, his reaction to the news is proof enough that he's got Irish blood in him, because he knows full well why he can't find out where he's from.

Via YouTube