The singer took to Instagram on Thursday to share a slideshow of snapshots of herself doing Simpson's make-up to turn him into punk rock icon Billy Idol.
Cyrus -- who ended up going as Idol's 1980s love Perri Lister -- mugged for the camera while applying Simpson's eyeliner in two of the pics before planting a kiss on her boyfriend in the last photo of the set.
"Makin up my man into baby billy idol!" Cyrus captioned the post.
She later shared a snapshot of herself and Simpson in their finished costumes, as well as a photo of the rock star couple they were dressing up as, to compare the looks.
"BILLY ? PERRI," Cryus wrote alongside the pair of pics.
She followed these up with two separate videos of her and her man. The first shows the pair playfully lip-syncing to Idol's famous tune "White Wedding," while the second basically just shows Cyrus and Simpson making out and groping one another as Idol's "Eyes Without a Face" plays in the background.
"It’s easy to tease but hard to get release…" Cyrus captioned the second clip, quotes lyrics from the Idol hit.