Celebs come out for preems

Room-wise, the after-party for Saturday’s AFI preem of “Carnage” may have been bigger than the actual production in Paris.

After the Chinese screening, guests moved from room to room at the Roosevelt Hotel, where pic’s John C. Reilly mused on the pros and cons of working on a small set.

“It was comforting at first to go to this nice apartment every day,” he began. “But then about week four I started feeling like I was going crazy … same costume, same people. It felt like actually shooting the same scene for six weeks, which was like a ‘Groundhog Day’ situation!”

AFI had such a crowded sked on Sunday that the Weinstein Co.’s “Butter” and “My Week With Marilyn” shared the Chinese red carpet.

“Marilyn” star Michelle Williams was asked how she’d spend a week with Monroe. “I would just be greedy,” said the actress. “I would lock the door of my house and have a sleepover for a week.”

Over at “Butter,” Jennifer Garner did double duty as star and first-time producer. In her latter gig, she had flown in one of the country’s top food sculptors to train the cast in butter carving, which helped relieve the work stress. “It’s incredibly relaxing, and if you mess something up, you just put more butter on top of it,” advised the thesp-producer.

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