Lisa Kudrow -- Good Genes or Good Docs?

Lisa Kudrow is serving up a Buffay of good looks.

Here's a 31-year-old version of the "Friends" leading lady at an event back in 1995 (left) and 22 years later ... the "Girl on the Train" actress in Hollywood earlier this year (right).

If we were giving her a grade ... it'd be an 'Easy A!'

The question is ...