Katy Perry and John Mayer sparked some new 'are-they-or-aren't-they' rumors over the weekend, when the two reunited at Katy's Memorial Day barbecue.

Perry threw a bash at her Hollywood Hills home on Monday and onlookers say the couple seemed to be enjoying each other's company.

"They seem to be back together-ish. They were very flirty and having a really good time together. They have good chemistry," a source told Us Weekly.

The Office stars Mindy Kaling and B.J. Novak along with 2 Broke Girls star Beth Behrs were spotted at the party, along with Katy's good friend Allison Williams.

The Girls star's boyfriend, Ricky Van Veen, is one of Mayer's closest pals.

Let the rumors begin...