From lace and leather-lovin' S&M madams in the pages of V Magazine to "Bitch I'm Madonna" #RebelBesties on screen, Katy Perry and Madonna are truly two inseparable sisters in pop — or, rather, one unapologetic mommy-daughter duo.

Madge's majorly successful, stripping nun-filled Rebel Heart Tour rolled into LA last night at The Forum in Inglewood. And, as with every other one of her shows, M invited one lucky fan onstage to join her in flipping off the entire arena for a rousing rendition of "Unapologetic Bitch."

And who better to do the deed than the nun-battling "Not Like The Movies" phenom herself, Katy?

Indeed, Katy was selected as Madge's victim of the evening — and she looked like she was having an absolute blast, breaking into entirely unrehearsed, yet entirely on-point choreography alongside the Queen of Pop.

"Well, that was unrehearsed but 💅🏼 ILY @madonna my 👑QUEEN👑," she wrote on Instagram.

And, after being gifted with the #RebelBanana for her good deed (which the two split on stage), Katy took the mic to give thanks: "I LOVE YOU, MOM!" she declared, as M burst into laughter. "Because all popstars are code "mom" #meta @madonna," Katy explained on Instagram. (Somewhere, Lourdes still has some questions.)

"Thanks, darling. I know you didn't want to come up here and do this. You're so generous," Madge deadpanned. Aww, these two!

And before Katy could leave the stage, she did what anyone would do in the presence of royalty — and bowed down to worship at M's feet. What a humble pop princess!

Even more amazing, though, were M-Dolla's parting words: "Bye bye, Katherine."

Here's hoping the friendship turns into one major duet on Katy Perry's PRISM follow-up. (A "Me Against The Teenage Dream," if you will.)

See Photos from Madonna's Rebel Heart Tour: