You know why Steve Martin doesn't age?

Because he's a vampire.  

Here's Steve circa 1989 starring in Parenthood, one of the most relevant movies of the decade which also produced a number of tunes about diarrhea that we still sing today.

And here's our main man in 2003 starring in Bringing Down the House, a movie you only need to see once because it gets worse and worse each time you watch it.

Almost 15 years later and still no difference. Fishy.