Ok that title's soooo bad but you see what I did there right? ;p
I think the joke's inspired by Mean Girls but I'm not sure because I've never seen Mean Girls (shame on me)

I love Paul's sweater vests! They look so adorable. <3
By the way what's your favorite Beatles song? That really interests me! Mine is eight days a week <3

If you can't read the picture:
John: Oh my God, Paul! I love your sweater-vest! Where did you get it?
Paul: It was my mum's in the 50's!
George: Vintage! So adorable.
Paul: Thanks!
...
John: That is the ugliest effing sweater-vest I have ever seen.