Megan Fox isn't even in the new 'Transformers' film, and yet she's still grabbing all the headlines as the movie hits theaters.

Shia LaBeouf just admitted in a no-holds-barred Details magazine interview that his romance with Fox continued off-screen. When asked how Fox's now-husband Brian Austin Green factored into that love triangle, LaBeouf could only say, "I don't know."

Now, according to an unnamed on-set source, the Megan-and-Shia hook-up happened while Fox and Green were on a 10-month break and she was a free agent. The couple, who'd dated for years, eventually married in June 2010.

Both Fox and LaBeouf have been vocal about the problems of making the previous 'Transformers' films, which is, allegedly, what helped the two bond: "Believe me, that was an unhappy set. I think they were drawn together because it was so ugly working on that film," the set source tells Us Weekly.

Oh, and for the (unverified) record, despite reports about Steven Spielberg demanding that she be fired, Fox was the one to walk away. "She was never fired," the Us source insists. "She said enough was enough and quit."

Who do you believe? And do you care?

[Via Us Weekly]