Marlon Wayans -- Bruce Jenner Should Just 'Get the Breasts Already'

Marlon Wayans believes Bruce Jenner's laryngeal shave is the first step toward becoming a woman -- but he's moving too slow -- telling Bruce, "Just get the breasts" already!!"

We broke the story, Bruce already consulted a plastic surgeon about reducing the size of his adam's apple -- though Bruce insists it's NOT the first step of gender reassignment, it's just because he doesn't like the way his throat looks.

Still, Marlon ain't buyin' Bruce's explanation -- and on his way out a "What the Funny" event he told us, "I think slowly but surely he's been turning himself into a woman all these years."

"Why don't Bruce Jenner just go and get the titties now ... just get the breasts."