Best of 2011: Hottest Hookups

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Scarlett Johansson and Joseph Gordon-Levitt

The pair were spotted making out in October. Three months before, they dined together in NYC's Soho area. "They first met about a film they wanted to do together, but it's gone beyond that now," a source told Us.

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Alec Baldwin and Hilaria Thomas

In August, the 30 Rock star confirmed he was dating a New York City yoga instructor. His brother Stephen told Us the star was "calmer" and "happier" with his much younger girlfriend.

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Ashlee Simpson and Vincent Piazza

After splitting from hubby Pete Wentz earlier in the year, Simpson began dating Boardwalk Empire actor Vincent Piazza in June. By September, he was introducing her to his parents!

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Ashley Greene and Reeve Carney

In early October, sources confirmed to Us that the Twilight actress was dating the star of Broadway's Spider-Man: Turn of The Dark.

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Blake Lively and Leonardo DiCaprio

After five months together, Lively and DiCaprio parted ways in October.

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Blake Lively and Ryan Reynolds

After splitting from DiCaprio, Lively moved on with Scarlet Johansson's ex-hubby. The duo shared romantic weekends in Boston, New York and Vancouver.

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Demi Lovato and Ryan Phillippe

Demi Lovato and Ryan Phillippe's age difference didn't keep them apart! An insider told Us, however, the duo's relationship was "nothing serious."

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Cameron Diaz and Diddy

In November, Diaz reunited with her on-and-off hookup since 2008. "Since then, when she's single, she'll booty call him," an insider told Us.

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Chord Overstreet and Emma Roberts

First linked in mid-April, the pair stepped out publicly for the first time in July in London.

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Emma Stone and Andrew Garfield

The Amazing Spider-Man costars began dating in June.

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Eva Longoria and Eduardo Cruz

Tony Parker's ex-wife told Us in March that things were "great" with Penelope Cruz's younger brother.

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George Clooney and Stacy Keibler

After splitting with Elisabetta Canalis, the actor began dating the former WWE star in the summer. He joked to E! News that Keibler "can kick my ass!"

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Jennifer Aniston and Justin Theroux

The Wanderlust costars began dating in the spring. "He's a charming young man," Aniston's father told Us. "I think they make a wonderful couple."

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Jennifer Lopez and Bradley Cooper

Although Lopez "liked the thrill" of Cooper pursuing her, according to a source, their romance fizzled by the fall.

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Jennifer Lopez and Casper Smart

Lopez and her backup dancer beau started dating in November. By Thanksgiving, Smart was spending the holidays with Lopez and her twins.

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Jessica Biel and Gerard Butler

The twosome found chemistry while filming comedy Playing the Field in Shreveport, Lousiana. Although the duo were heavily flirting in March, a source told Us Biel "only wants to be friends."

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Kate Winslet and Ned Rocknroll

The Oscar winner met Rocknroll in August at Sir Richard Branson's Necker island home. She famously helped Branson's mother, Eve, escape a house fire during the tropical getaway.

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Kristin Wiig & Fabrizio Moretti

The SNL star was spotted making out with the Strokes drummer in December. "They were all over each other," a source told Us.

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Lady Gaga and Taylor Kinney

The pop star met the hunky Vampire Diaries star on the set of her "You and I" video in July. "They're hooking up and getting to know each other," said a source close to Gaga. But the pair -- who were spotted leaving NYC's Alvin Ailey dance studio in mid-October -- aren't serious.

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Pia Toscano and Mark Ballas

The Idol contestant and Dancing with the Stars pro dated for six months before splitting in September. "[Mark's] high school drama was a little too much for Pia," a source told Us.

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Olivia Wilde and Jason Sudeikis

The actress and the SNL star weren't shy about hiding their romance in December, when they attended a show afterparty holding hands.

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Paul McDonald and Nikki Reed

After just two months of dating, McDonald and Reed confirmed their engagement to Us in June. In October, they said "I do" at a private ranch in Malibu, Calif.

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Pete Wentz and Meghan Camper

In September, the rocker stepped out with his model girlfriend in L.A.

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Alex Pettyfer and Riley Keough

The Magic Mike costars fell for each other on set.

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Ryan Reynolds and Charlize Theron

Reynolds and Theron had a brief summer romance that ended in July. "He only wanted something casual, but she's in a rush to settle down, have kids and start a family since she's getting older," a source told Us.

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Scarlett Johansson and Sean Penn

The couple's May-December romance lasted for five months until Penn dumped Johansson in June. A source told Us the actor has not wanted anything "serious" since his 2010 divorce from Robin Wright, adding, "Scarlett pursued him."

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Vanessa Hudgens and Austin Butler

Zac Efron's ex was first spotted with Butler in September at Ashley Tisdale's sister's birthday party.