I wonder if Dawson Casting is quite right though. I'm thinking here of an actor playing a man in his mid 20s, but looking much older. Whether he was or not, I'm not sure, but flipping through Wikipedia's transcripts of the opening narrations of the first season episodes, I see:

E21 has Vera Miles playing a 25 year old when she's 30.

E31 has George Grizzard playing someone in his "youthful 20s" when he's about 32 and looks it.

Seems similar, but also different: older actors playing younger people.

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