Do you remember a character on Friends, a girlfriend of Chandler's who seems you!

Do you remember a character on Friends, a girlfriend of Chandler's who seems young but nobody knows her age?

I seem to remember Chandler doing several of his double takes everytime she references something old fashioned, and the entire episode was spent with the rest of the group trying to guess her age.
Or maybe it was Seinfeld?

I'm going crazy!

I remember Ross having a student as a girlfriend . Her dad was played by Bruce Willis and he ended up dating Rachael . Ross gave up his young girlfriend because she was way too immature .