Valerie Harper -- Good Genes or Good Scarves?

It's hard to wrap your head around how well Valerie Harper has aged.

Here's Bethenny Frankel the 36-year-old "Rhoda" star back in 1976 (left) -- and 37 years later, the 73-year-old "Valerie" (which later became "The Hogan Family") star in L.A. this week (right).

She's irreplaceable.