Not exactly theme songs, but so far Mensa's favorites are ones where the vocalist whistles.
She likes Paul Simon's "Me and Julio Down By The School Yard" and "Jealous Guy" She likes Bryan Ferry's rendition better than the original John Lennon version.
Mavis' favorite song was "Mademoiselle Nobs" by Pink Floyd. That's the one where the guitarist plays blues-harmonica and an Afghan Hound provides the vocals by howling. Everytime Mavis heard it, she would sing (howl) along.
The only place I've seen it was on Pink Floyd's "Live at Pompeii" DVD.