Katy Perry Crashes Wedding With Robert Pattinson, Then Reunites With Ex John Mayer At Her Memorial Day Party

Katy Perry had a busy Memorial Day Weekend.

The singer was spotted crashing the wedding rehearsal of two strangers near Santa Barbara, with good friend Robert Pattinson as her partner-in-crime.

One of the guests of the wedding, Stephanie Sands, told People that the  celebrities were "just sitting next to each other watching the wedding rehearsal in the main courtyard area" at a ranch in Montecito.

"They were dressed very casually," Sands said. "She was wearing a hoodie and big sunglasses. There was no PDA between them and no body language that showed they were dating. They just sat together and watched."

Stephanie commented that she had "no idea" what the friends were doing at the wedding party, since they were not invited and were not mingling with guests.

Katy Perry, 28, also hosted a Memorial Day party at her new Hollywood Hills home and invited a few friends, including John Mayer, 35, her ex as of two months ago, according to Us Weekly.

Does this mean the couple is getting back together?

One witness told Us Weekly that Perry and Mayer "seem to be back together -- or back together-ish."

"They were very flirty and having a really good time together. They have good chemistry," the source added.

Another witness said the pair "were definitely friendly."