While it is still needs a title, Nancy Meyers' upcoming film boasts an unbelievable ensemble of talent -- including Meryl Streep, Alec Baldwin, and Steve Martin. Only ET is on the set of the untitled film, where the stars reveal some of the plot details and take a stab at naming the romantic comedy!

It's a rare look at a Meryl movie as it shoots, and ET has learned the Oscar-wining actress plays a baker in the film, Alec plays her ex, and Steve is the architect designing Meryl's character's new house -- and the three are in a love triangle.

The film is being helmed by writer/director Nancy Meyers, who has worked her magic in such memorable flicks as 'Father of the Bride,' 'The Parent Trap,' 'What Women Want,' 'The Holiday' and 'Something's Gotta Give.'

So what's the plot behind this star-studded romantic comedy? Watch the video to hear the scoop from the cast, and find out if Meryl plans to make an appearance on co-star Alec's hit TV show "30 Rock."

As for the film's name, Nancy tells ET she usually figures out the titles for her films at the last minute, and once she's named the project, she says ET will be the first to know!

The star-studded film will hit theaters on Christmas Day.