It started off as an Upper Midwest, folk music-oriented take on The Grand Ole Opry before heading off in its own direction.
On the flip side, The Vinyl Cafe clearly took inspiration from APHC but eventually evolved its own style. In the US, some public radio stations even air The Vinyl Cafe immediately following APHC.
Hilarious in Hindsight: Garrison Keillor's "I'm A Lutheran", from the 1990s, makes a lot of jokes about Episcopalians and how Garrison likes Lutherans more, Garrison Keillor is one of them (an Episcopalian) now.
Memetic Mutation: Keillor's red socks, invariably seen at the live shows. They're something of a personal trademark of his.
Leading to a joke among some fans that Keillor will only retire when "he runs out of red socks"
More Popular Spinoff: Keillor hosted the weekday morning show on Minnesota Public Radio starting in 1969. After writing an article about the Grand Ole Opry in The New Yorker in 1974 he decided to try his own Saturday night live music variety show. He did both shows for a while, but the Saturday show was a big hit in Minnesota and became nationally syndicated, so Keillor quit doing the weekday show in 1982.
Never Live It Down: The "Penguin Joke" became a Running Gag because the first time Garrison Keillor tried to tell it on the air, he badly flubbed the delivery. They've been repeating his mistake word-for-word ever since.