Jennifer Aniston & Justin Theroux: From Costars to Engaged Couple

Jennifer Aniston is getting married!

Justin Theroux popped the question Friday and the actress, 43, happily accepted. Fans of the duo shouldn’t be surprised – it’s been a fabulous 15 months for Aniston and Theroux, 41, who first met while filming Wanderlust in May 2011.

Here’s how they went from costars to engaged couple.

Charlie Day: 5 Things to Know About the Horrible Bosses Star

He’s the breakout star of Horrible Bosses, fighting off Jennifer Aniston’s advances – and getting a little out of it during a certain vacuum scene.

Still, fans of FX’s raunchy hit, It’s Always Sunny in Philadelphia, already know actor Charlie Day, 35, as the show’s lovable (but oh-so-weird) Charlie, whose character has a penchant for killing rats in the basement of Paddy’s Pub and dressing up in a neon green leotard as the unofficial mascot of the Philadelphia Phillies, Green Man.

Charlie Day, Mary Elizabeth Ellis Expecting a Baby

It’s been a good year for comedian Charlie Day. His film Horrible Bosses is a hit at the box office, and he’s going to be a dad.

“We’ve got a kid due in December,” Day, 35, confirmed to PEOPLE at a Maxim and FX party at San Diego Comic-Con Friday night. “We’re five months along, and she’s feeling great. We’re excited.”

Day and his wife Mary Elizabeth Ellis, 32, who stars alongside the actor as “The Waitress” on It’s Always Sunny in Philadelphia, consciously decided to expand their family, says the comedian.

Jennifer Aniston and Justin Theroux's Post-Premiere Date Night

They may not have made their red carpet debut together at Thursday’s Horrible Bosses premiere in Los Angeles, but Jennifer Aniston’s boyfriend Justin Theroux was there to keep her company.

After meeting up inside the premiere, the couple hit Chateau Marmont just past 10 p.m. with a large group of pals, including Aniston’s BFF Courteney Cox and Chelsea Handler.