"Ah," indeed. Bewitched is a classic American sitcom about advertising executive Darrin (not "Darren") Stephens and his wife Samantha, who happens to be a witch. Darrin was played by Dick York, up until 1969 when he left the cast due to illness. He was replaced by Dick Sargent, with no explanation or reference to his changed appearance.

The same trick has been used in several other TV shows since, notably in Roseanne when the character of Becky switched from being played by Alicia Goranson to Sarah Chalke. In the episode in which the switch occurred, there were a few semi-fourth-wall-breaking comments to Becky having changed her appearance. But the best bit was during the closing credits, when the family is watching TV. It turns out they are watching Bewitched. Roseanne comments that she doesn't like they way they changed the actor who played Darrin. When everyone else agrees, Becky says that she likes the new Darrin.

But you won't see anything that contrived in Irregular Webcomic!