Actors who shouldn't sing

I just saw Ron Howard, when he was "merely" an actor, before he became a director, still a kid, fresh off his "Opie" days on The Andy Griffith Show, sing a couple tunes in The Music Man. He fearlessly, shamelessly belted 'em out, but jeez--his voice was off-key! He even told director George Lucas during the casting of American Graffiti "I can't sing and I was told this is a musical", to which George cryptically replied "It is a musical and it's OK that you can't sing". American Graffiti's soundtrack is a musical compilation of original period songs from the '50s and '60s sung by many, many period artists.

Christopher Plummer sang Adel Vie (I hope I spelled that correctly) and the main title song from The Sound of Music, and reportedly did a pretty good job, but was still dubbed over by another singer who apparently had better singing chops.

I've tossed this subject around on other boards; I jokingly asked 'What's your favorite Robert Mitchum song?' Thinking that 'The Ballad of Thunder Road' was the only song he ever recorded. Then I found out that 'Triangle Man' had recorded multiple albums!

If you've ever heard They Might Be Giants' song 'Particle Man,' it was apparently all inspired by the two Johns watching Robert Mitchum in an old movie, and one of them said "Bob really looks like a triangle, doesn't he?"

- What are you gonna do, when the world catches on?

I just saw Ron Howard, when he was "merely" an actor, before he became a director, still a kid, fresh off his "Opie" days on The Andy Griffith Show, sing a couple tunes in The Music Man. He fearlessly, shamelessly belted 'em out, but jeez--his voice was off-key!
Wasn't that on purpose?

A bunch of actors in MAMMA MIA! don't sing well, but Pierce Brosnan stands out as the worst.

Shatner

Ansel Elgort. I like his acting but his singing? Not so much.

Cameron Diaz, Jennifer Lawrence, Hugh Jackman, Gerard Butler, and Ben Affleck. I've heard all of them sing on camera, and they really suck.