OMG you must watch Sunset Boulevard. Still, all these decades alter, the best Hollywood-on-Hollywood movie ever, and despite stiff competion by several of his other movies Billy Wilder's masterpiece.

...wow. I mean, I get it, he's super hot, but... ugh.

The white t-shirt Brando is wearing as Stanley became colloquially known as a "wifebeater". It wasn't meant derogatory, which is something else again.