Memorial Day Weekend has come and gone and along with it many backyard barbecues with friends and family. Katy Perry also had a Memorial Day BBQ and who was in attendance? Well, none other than her ex-boyfriend John Mayer! Did any of your exes attend your cookout this weekend? We didn't think so...

When she wasn't hanging with R. Patz and crashing wedding rehearsals, Katy was playing hostess at her brand-spanking-new house in Hollywood Hills to her friends, which included John Mayer. Say what?!

One doesn't typically invite their freshly broken-up with ex-boyfriend to a party at their house unless there's some sort of reconciliation goin' down. A source at the party told US Weekly, "They seem to be back together -- or back together-ish. They were very flirty and having a really good time together. They have good chemistry." Back together-ish, huh? Or as some would call it "remaining friends."

The pair broke up back in March amid speculation that Katy Perry wanted their relationship to progress in a more serious direction. There were also rumors that Johnny boy sent Katy's BFF Rihanna some flirty texts and tested Girl Code to the fullest. RiRi knows not to go down that road!

So are they or aren't they? Our guess is they are trying to remain friendly.