Katy Perry joined Madonna on stage on Tuesday night (27.10.15) to toast her latest 'Rebel Heart World Tour' concert with a shot from a banana bottle.

Katy Perry and Madonna on stage at The Forum

Katy Perry and Madonna on stage at The Forum

The 'Roar' hitmaker surprised fans at the sold-out Forum in Los Angeles when she joined the Queen of Pop during her set closer 'Unapologetic Bitch' along with Diplo and Anderson Cooper.

Firstly, Katy twerked against Madonna as the legend playfully slapped her butt and then performed a series of sl*t drop dance moves around her fellow music minx.

Katy, 31, couldn't contain her excitement at getting the chance to gyrate with Madonna, 57, and grinned from ear-to-ear and giggled as finished twerking before grabbing the microphone from her idol and jokingly shouting "I love you mom".

The pair then celebrated the show by each taking a swig from the unusual fruit-shaped container, although Katy looked unsure before downing the mystery drink she shouted "It's Tuesday? See you on Friday!" and then took her gulp.

Following her impromptu appearance, Katy posted on her Instagram account: "Well, that was unrehearsed but ILY @madonna my QUEEN ... Because all popstars are code "mom" #meta @madonna #Repost @tiersz (sic)"

Madonna was just as thrilled as Katy with their dance-off and drink.

She wrote on Twitter: "Sharing a Banana with Katy Perry!! Highlight of my show at the Forum! Thanks Katherine ... Best Unapologetic bitch ever! Thank you Katy! Thank you L.A. (sic)"