When JENNIFER ANISTON’s hunky actor/fiance JUSTIN THEROUX – who’s penned such screenplays as “Iron Man 2,” “Tropic Thunder,” and “Zoolander 2” – suggested they co-write a comedy movie, Jen nixed the idea, saying: “No, I’m not a good writer!”

But Justin persisted, showering her with compliments, saying how funny she is – and how witty they are together – finally convincing Jen to take a shot at it.

Said an insider: “They worked out a story idea and a list of characters, and when Justin went away on a job for a week, Jen was so inspired she just kept on writing – alone! Excited by her work, she thrust the pages at her honey the minute he was back and gushed, ‘I can’t wait for you to read this!…I think it’s really good!’

"After reading the pages, Justin stared stone-faced at his future wife and started mumbling stuff like, ‘Er…it’s…okay, but it needs…it’s not quite, er…!’ Jen got the message loud and clear, shrieking, ‘Are you kidding me? You’re the one who pushed me to do this. I told you I wasn’t a writer!’ Justin wisely zipped it as Jen angrily ripped up her pages and stormed off!”