Actresses Allison Janney (The West Wing) and Christine Lahti (Chicago Hope) have a very similar look. This was mentioned as a quick joke on Studio 60, on which they both guest starred.
Actor David Doyle from the original Charlie’s Angels series and actor Tom Bosley from Happy Days looked amazingly similar sometimes and tended to confuse people into thinking that the same person played both roles.
When I was little and used to watch reruns of Mama’s Family it wasn’t until the first time I saw Eunice appear that I realized that Carol Burnett wasn’t playing Mama.
Now that I think about it, at some point before I saw Carol Burnett as Eunice, I saw Vicki Lawrence do Mama’s voice out of costume, and that’s what got me to start wondering about it, but even with that I still thought Carol was Mama and that Vicki was just showing that she could do the voice to…or something like that.