Apologies for the double post, but I was watching "Lucy and the Good Skate," today, another superior third season installment. For anyone who is interested, Garry Marshall talks about this episode in his autobiography - which is definitely worth checking out. Marshall writes that he and his writing partner, Jerry Belson, had written a script that Lucy performed at a charity event in 1964 or 1965. When Milt Josefsberg took over, he remembered them from the charity event, and they were brought aboard. Initially, Garry Marshall didn't want to do it - he had done a couple of scripts for the Dick Van Dyke Show, and at the time, it was considered to be the "classier"/more sophisticated show. But Garry Marshall's wife had just had a baby, so Milt Josfsberg convinced him that The Lucy Show would give him greater job security/better exit opportunities.
With regard to "Good Skate," Garry Marshall notes that the first draft was very different, and that Lucy didn't like it at all. She wrote "this is shit," on the cover, and handed it back to him. Lucy didn't think it had a strong enough climactic ending, so Marshall and Belson came up with the finale where Lucy keeps running into things on skates while at the party. Marshall notes that Lucy wasn't interested in plot or believability at this point - she just wanted the slapstick that the audience loved, so that's what the writers gave her.
Later in the book, Marshall adds that many of the sitcoms that he wrote and developed in the 1970s - The Odd Couple, Happy Days, Mork and Mindy, etc. borrowed heavily from his work on The Lucy Show. In fact, his later show, Laverne and Shirley, was essentially a homage to his work with Lucy and Viv.