Michael Bay announced on his blog today that Megan Fox has been cast in the Teenage Mutant Ninja Turtles film. This came as a surprise to many after Fox, who starred as the main love interest in his first two Transformers films, was written out of the third. Bay's short and cryptic blog entry simply says "TMNT: we are bringing Megan Fox back into the family," not specifying who she will play. Naturally, speculation would lend to her playing April O'Neil, the long-time ally of the Turtles (and famous for her yellow jumpsuit in the original animated series).
Bay's adaptation of the Turtles franchise has been met with criticism from fans for originally stating that the Turtles would now be aliens rather than mutants. Since then, Bay has publicly involved TMNT creator Kevin Eastman in production. A version of the script was leaked online shortly after, which showed significant changes to the Turtles. However, none of this information can be linked with the film now, which will begin filming later this year, as changes and revisions are inevitable. As it stands, Megan Fox is pretty much the only definite information.