ideas for their wedding

An onlooker told E! News: "People in the audience turned to each other perplexed and said, 'Wife?'"

There's also been rumours they've secretly tied the knot.

However, MGK was still teasing his "weird" plans for their nuptials to press.

Speaking to E! News at the bash at Las Vegas' MGM Grand Garden Arena, he

said: "I don't want to say too much.

"It's going to be weird. It's going to be completely out of the box."

Asked his fiancée thinks of his unusual ideas, he replied: "She's a genius.

"You know what I'll say? I'll throw the reel out really far, and then she'll reel it back in if it's too far."

The 'Bloody Valentine' rocker was then asked if he'd consider copying pals Kourtney Kardashian and Travis Barker and practicing with an unofficial Vegas wedding after the BBMAs.

However, they were celebrating the 'Jennifer's Body' star's 36th birthday (16.05.22) instead.

He responded: "Well, it's my fiancée's birthday at midnight.

"So, we're celebrating her wonderful life being here on planet earth."

The 'Transformers' actress then added: "I'm boring I don't drink, but I'm sure he'll go off for me."

Megan is mum to three boys, Journey, five, Bodhi, eight, and Noah, nine, with her ex Brian Austin Green, while Machine Gun Kelly has a 12-year-old daughter named Casie from a previous relationship with Emma Cannon.

The couple have yet to comment on the baby rumours, but a source claimed that although the pair would love to start a family together, they plan to wait a few more years.

The insider said: "Megan would love to have a baby with MGK ... they've already discussed it ...

"(But) they both want to wait a couple of years. They're having way too much fun right now."