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.