Well, that was fast. It seems like just yesterday (and it almost was) that we were all gagging over Katy Perry and John Mayer’s debut as the perfect gross couple as they cavorted for the paps in front of Chateau Marmont in early August. Since then, we’ve heard that they “could be the real deal” and that Katy trusted John so much that she just knew he’d never write a song about her. It’s a good thing John doesn’t have a new album coming out soon, or that theory would be tested in short order. Us Weekly has a story about how John and Katy have broken up, and they were (supposedly) actually dating for a whole two months, but it’s over now:

Talk about hot and cold.

After a couple months of casual dating, John Mayer and Katy Perry have split, multiple sources confirm to Us Weekly.

“She’s really upset about it,” one insider tells Us.

Echoes another insider: “She is making it seem like it wasn’t serious with John, but she is hurt.”

Us Weekly first reported the budding romance, with Perry, 27, and Mayer, 34, making an “affectionate” appearance together at Soho House in West Hollywood June 19.

At a Beverly Hills pool party Aug. 4, recently divorced Perry and notorious Lothario Mayer “were all over each other, making out,” one observer said.

A pal said earlier this month that the “Teenage Dream” singer was ready to get serious with Mayer. “She doesn’t want to get her heart broken again, but she feels a real connection and wants to see where things go” with Mayer, whose exes include Jennifer Love Hewitt, Jessica Simpson and Jennifer Aniston.

Perry divorced Russell Brand earlier this year, and briefly dated Florence + the Machine rocker Robert Ackroyd in the spring.

[From Us Weekly]

Hmm, I wonder what happened. My initial guess is that Katy might have pushed for a full-blown relationship, and in return, John pushed her away. I could be wrong though. Maybe Katy is actually the one who broke it off with John after he wouldn’t stop hogging the bathroom mirror. The dude is (unnecessarily) vain. Or maybe she got turned off after finding out that his onstage “O” face is the same as his bedroom “O” face. Nasty!

Update: People has confirmed the split, and Radar adds that John did the dumping: “John did a real number on Katy. She held off from his advances for the longest time, but he laid on the charm thick and promised her he was a changed man. She eventually gave in, fell head over heels for him and then – yep – once he had made his conquest, he dumped her.” What a douchebag. I can’t believe anyone dates John when this has always been his game.

In (now) vaguely-related Katy news, it seems that Russell Brand can’t keep a relationship together either. That is, he can’t keep it in his pants. According to a story in this week’s Star, Russell has already cheated on his current girlfriend, Isabella Brewster:

Looks like recovering sex addict Russell Brand may need to head back to treatment. The British comedian, 37, who’s been dating 30-year-old talent agent Isabella Brewster for two months, was busted kissing a blonde mystery woman in the early morning hours of Aug. 6. An eyewitness tells Star that Russell stepped out of his Range Rober, still in his pajamas, with a messy, “sexed-up” look that can only come after a roll in the hay. And the blonde riding shotgun was definitely not Isabella!

“He opened up the back door to grab the woman’s bag, then proceeded to kiss her on the lips, stroke her hair, and give her a lingering hug before hopping back in his car to drive away,” adds the bystander. “They definitely looked like more than friends.” You think?

[From Star, print edition, September 3, 2012]

I hate to say it, but one really shouldn’t expect fidelity while dating Russell Brand. Honestly, I don’t think it’s possible for him to just have one woman on a long-term basis. You know what Rusty needs? His very own bona fide harem. The timeline of this story quite damning though. Rusty was supposedly all over the blonde on 8/6, and here he is outside the Tate Modern museum in London (with Isabella) on 8/8. What a dog.

Photos courtesy of Pacific Coast News, Fame/Flynet, and WENN