The bulk of this episode is built around twin brothers, played by John Ringham, and an endless game of telephone problems across three locations and one brother’s unfortunate wife, hanging up on each other, calling back before the other has put down the receiver, and so on. Our son absolutely adored it and laughed through the phone silliness, except he was really unhappy when one of the brothers “steals” Catweazle’s familiar, the toad Touchwood. Because Touchwood is not feeling good and not eating, he and Cedric take him to a zoologist in the village. It turns out Touchwood’s species has been extinct for hundreds of years and they think it’s a great discovery.
The phone shenanigans reminded me of a terrific gag about Call Waiting in the second episode of Ellen / These Friends of Mine in 1994. I pulled it up on YouTube to show our son the setup to the gag so he could laugh about how silly and strange landlines and all their “Custom Calling Features” were. I didn’t actually show him the gag itself, in which Ellen unwittingly insults Clea Lewis’s character, because it’s really a crueler humor than I’d like our kid to see so young, but the horrified noise that Ellen makes once she realizes what she’s done is extremely funny! The scene is about two and a half minutes into this clip, if you’re older than our kid.
Fire Breathing Dimetrodon Time 
It occurred to me later that our son getting so upset about Touchwood being stolen was very much like the part in the Space Academy episode “Planet of Fire” when Peepo gets picked up and carted off by an alien guy!