What are some of the worst actor miscasts in TV?

There was a British series called Urban Myths that cast the bearded Commander from Handmaid's Tale as Michael Jackson

Did the episode ever actually air? I see online that it was pulled, but it's not clear if it actually aired. I'd be really curious to see it.
It's Joseph Fiennes, not Bradley Whitford. Had to look it up.

Brian Bonsall as Alexander in Star Trek The Next Generation.

The role was poorly thought out and written, that's not his fault, but the kid always looked wildly uncomfortable in the loaf and couldn't act at all.

They had 5 separate actors play the character so it seems like they were desperately trying to fix the issue.
- Hey I'm actually baffled by your reply. You clearly didn't know there were 5 actors who played Alexander, because if you did, you'd know they were mostly one offs, from a different series at a different age or, uh, a photograph. It's like you saw my comment, decided to reply to it, searched "Star Trek Alexander actor" and read the headline of the first result, a Screen Rant article titled "Star Trek: All 5 Actors Who Played Worf's Son, Alexander", and decided "That's enough info, I'm ready to reply to that comment."
  Clearly you didn't read the article, otherwise you wouldn't reply the way you did, because you'd know why there's 5 Alexander's and it wasn't because the writers were trying to fix the issue.
  I'm not mad or annoyed or anything, I'm just utterly baffled by how you use the internet.
- That's.. not quite right. Did you get this from skimming Wikipedia? It's true that the first TNG ep featuring Alexander had someone other than Bonsall play the role, that kid stopped acting almost immediately after. Bonsall played Alexander for the rest of TNG. They age up Alexander significantly for his return in DS9, so, yeah, needs a different actor. There's a TNG ep where Alexander comes back from the future to try and correct what a shitty character they made, so that's probably your "fourth" Alexander and I'm not sure where the fifth comes from.
  Edit: Looked that one up. The "Fifth Alexander" is a technicality. Worf has a picture of him and Alexander as one of his personal effects that he brings with him onto DS9 and the person in that picture "playing" Alexander is uncredited, but makes no other appearance other than being in that photo.
Everyone I see him I feel like he's trying so hard to disappear. Just will it into existence.
- Star Trek has always struggled with child actors, but I think Bonsall was really just too young to handle the role. In part, I think the writers realized this and tried to cut him out, but this lead to the issue of making Worf look like a horrible father, so they bring him back and repeat.
  He was a child so I can't put any blame on Bonsall, but I truly think it was a serious mistake to cast him for that.

Mel Gibson in The Continental.

I would have given it a chance otherwise.