Scarlett Johansson: Ms. May-December

March 31, 2011 — -- She's only 26. She's one of young Hollywood's fastest rising stars. But when it comes to matters of the heart, Scarlett Johansson leans older. Much older, almost twice-her-age older.

Johansson seemed to publicly debut her relationship with Sean Penn, 50, last weekend at Reese Witherspoon's wedding.

After the Oscar-winning actress tied the knot with talent agent Jim Toth, Johansson and Penn reportedly hit the bar at California's Ojai Inn & Spa to nuzzle and nosh on pizza, a club sandwich, and gin and tonics.

According to Usmagazine.com, after their table was cleared, Johansson hopped on Penn's lap and made out with him for 15 minutes. With that plus the couple's trip to Cabo San Lucas, Mexico, earlier this month, it looks like Johansson has booted her estranged husband, Ryan Reynolds, 34, out of her love story and re-cast him with a more seasoned leading man. (It's the romantic equivalent of trading a can of Coors Light for a 1992 Screaming Eagle.)

Johansson isn't the only star seemingly in love with the idea of a May-December relationship. Below, check out three other recently minted couples with decades between them.

Kelsey Grammer and Kayte Walsh

Last year, the erstwhile "Frasier" star, 55, sped up a bitter divorce with his ex-wife, Camille Grammer, evidently for one key reason: so he could marry his new object of affection, Kayte Walsh, 29.

Grammer met Walsh, a flight attendant for Virgin Atlantic, on a plane to New York before he started divorce proceedings with his wife.

While they may have been smitten at 30,000 feet, things didn't go so smoothly on the ground, where Grammer engaged in a public war of words with his soon-to-be ex-wife and Walsh suffered a miscarriage.

But it was all smiles on Feb. 25, when Grammer and Walsh exchanged vows at the Longacre Theater in New York City. The ceremony was followed by a reception at the Plaza Hotel that featured a four-course dinner -- appropriate given that Walsh is Grammer's fourth wife.

Their relationship may have inspired Johansson and Penn's recently display of PDA: In October, Armisen and Elliott reportedly were caught making out at the New York City wine bar Riposo 72.

Jim Carrey and Anchal Joseph

In 2010, when Carrey and Jenny McCarthy split after five years, the funnyman seemed down. He took to Twitter late at night to post erratic musings about cyclopses, a big blue ball and his sanity (or seeming lack thereof).

In January, he snapped out of his funk. Carrey, 49, hit the town with Anchal Joseph, 24, a former "America's Next Top Model" contestant, clutching her hand as they left a performance of Laura Linney's New York City play, "Time Stands Still."

Carrey's rep didn't respond to ABCNews.com's request for comment about whether he and Joseph are still an item, but judging from his Twitter feed, he's feeling pretty good about someone. "Mmmmm... it's heaven waking up beside you!," he wrote on Monday. "Let's just call in sick and make love all day...after we brush our teeth of course! ?;^B)"