Wow. That was quick! After just three months of dating, Scarlett Johansson and her much-older beau Sean Penn are cohabitating.

The 26-year-old divorcée “has essentially moved in over the last few weeks,” an insider told Us Weekly, trading in her temporary accommodations in a West Hollywood hotel for Penn’s $3.8 million Malibu home.

Since the unlikely couple started shacking up, they haven’t been seen out on the town as frequently.

“They just stay home,” the source explained, preferring to eat in and spend time with Penn’s children from his marriage to Robin Wright. (They’re not exactly “kids.” Daughter Dylan is 20 and son Hopper is 17.)

The couple has also done some entertaining. Their guests have included Javier Bardem and Owen Wilson.

Wilson was photographed jogging with the couple last weekend. You remember those pictures, right? They were the ones that started tongues wagging about whether Johansson is pregnant. Her rep nipped that rumor in the bud a couple of days later. (Or tried to. I’m still stuck on that misleading shirt placement thing.)

It all just seems a little quick to me, though. I mean, it’s only been four months since Johansson split with hubby Ryan Reynolds. And at 50, Penn’s almost twice her age!