Kristen Bell -- Good Genes or Good Docs?

Kristen Bell's good looks are frozen in time!

Here's a 24-year-old version of the "Veronica Mars" star at an event back in 2004 (left), and 13 years later ... the now 37-year-old mother of two looking like the Arendelle Princess at The Beverly Hilton last month (right).

No SAG here.

The question is ...