Strange actor choices

Another thread got me thinking about how some casting choices in films can be real headscratchers. What casting choices never made sense to you?

I understand that it was intentionally bizzare, but I still can't get over Christian Slater's portrayal of a rapping Winston Churchill.

When I was in school Gina was chosen to be in the school nativity play. That's okay.

But it's not okay. She played the role of Jesus.

Matt Damon / Loki

When I saw in the movie the first time, I thought it was a minor part of an actor portraying a cosplayer.

When Belushi & Aykroyd reversed roles (in Neighbors).

Oh yeah, and Max Showalter in Niagara. The other three leads are fine, but he's just a great big doofus throughout.

I like Robert Downey, Jr., but did not understand his take on Sherlock Holmes.

Where did Sherlock Holmes pick up Wing Chun?

Anne Hathaway in Interstellar.
She was playing herself instead of professional smart astronaut.

#7 A manic, drug-addicted dude who likes to fight? I think he was playing to type! (I haven't actually seen that movie, just having fun).

For my own choice: Kevin Costner, Robin Hood: Prince of Thieves. When you're singularly responsible for a Mel Brooks spoof, you know it's bad.

Runner-up: Idris Elba, Mandela. Honestly, when you think Nelson Mandela you think of a man who has the weight of decades in prison, who is responsible for many atrocities, trying to right a terrible wrong through more peaceable means as he ages. You don't think of a well muscled hunk with make-up. All I kept seeing was John Luther, or Stringer Bell.

Notable Kevin Smith choice: Michael Keaton, Batman. How the hell are you going to cast Mr. Mom as Batman? Of course Keaton killed it, but at the time I can understand how people were shocked.

I've noticed that on every biopic (about men) I watched, the main character's wife is always a cute sexy girl, even though their actual wife weren't especially pretty in real life.