Dr. Twombly's office is actually a re-dress of Mr. Drysdale's office.
Elverna Bradshaw must have two daughters because Pearl said that the man who was supposed to marry Jethrine ended up marrying Elverna's daughter. But in season 8, "Bigmouth" Bradshaw gets married to Robert Holloway.
(Granny is questioning Dr. Twombly and his medical knowledge)
Granny: How do you cure Quinsy?!
Twombly: Quinsy? Oh, Tonsillitis.
Granny: No. That wouldn't cure it.
(Jethro comes in with a busted tire)
Jed: How'd that happen?
Jethro: Well, I was blowin' air into it like this here. (blows air in the nozzle) When all of the sudden, POW!
Pearl: Jethro, I told ya and I told ya: use the pump. You always bust the tires when you blow em up by mouth!
Twombly: Well, good-bye folks. It's been weird!
(The clan is trying to come up with a doctor Jethro can visit to get examined by)
Pearl: Trouble is we don't know no doctors.
Elly: Well, I know the critter doctor over to the zoo.
Pearl: Jethro's a human being, Elly May.
Jethro: Thank you, Ma.