When John Lennon offers Paul McCartney the chocolate, he says "Take this, brother. May it serve you well." This is a direct quote of a line Lennon spoke in the background to the song "Revolution 9" and in the scene, it is meant to be a joke between the two.
On the Adam Buxton Podcast in late 2020, Paul McCartney claimed he "enjoyed the film" and wished it would've happened "like that".
After John kisses Paul in the elevator, Paul asks John "Is my name Brian?" This is a reference to Brian Epstein, the gay manager who was rumored to have had a sexual relationship with John Lennon (although McCartney has rubbished this suggestion).