Kim Kardashian Had Trouble Squeezing Into Marilyn Monroe Dress

Kim Kardashian rocked Marilyn Monroe's iconic dress at the Met Gala ... but, the struggle was real, when it came to actually getting into the iconic garment.

Kim and her boo, Pete Davidson, hit up Ripley's in Orlando 10 days before the NYC shindig ... and it was a whole process getting it to properly fit.

Check it out ... it takes several minutes and all hands on deck to help her get MM's "Happy Birthday, Mr. President" dress over her butt.

It's funny ... at first, Pete chats with her from the sidelines, before jumping in to help ... imploring her to relax and breathe.

The basic problem -- the dress wouldn't zip over her butt, and she couldn't alter it. So, the solution ... a white, vintage fur coat that draped over the zipper which was only partially fastened.

Here's the thing ... Kim wore the real MM dress on the red carpet, but then scurried away into a room to change into a replica dress that fit a lot better, and that's what she wore during the event.

BTW ... the real dress apparently was never cleaned after Marilyn wore it ... hence some dirt marks at the very bottom of the dress.

Ripley's gifted Kim a jar of Marilyn's hair, and in the video she says she's gonna sleep with it every night, adding, "Sorry Pete!" Pete laughed out loud ... clearly not threatened!