Johnny Depp and Amber Heard
Actor Johnny Depp and his fiancee, model Amber Heard, arrive at the Metropolitan Museum of Art Costume Institute Gala Benefit celebrating the opening of "Charles James: Beyond Fashion" in Upper Manhattan, New York, May 5, 2014. REUTERS/Lucas Jackson

While filming their upcoming movie "The Adderall Diaries," costars Amber Heard and James Franco are allegedly getting very close on and off the set that fueled recent breakup rumours between Heard and fiancé Johnny Depp. There are whispers around the net that the "Pirates of the Caribbean" star is getting cold feet about tying the knot with his 28-year-old bride-to-be.

"There's a real spark between Amber and James, and Johnny was jealous as hell when he saw pictures of them cuddling and giggling," an insider told The National Inquirer. "Although Amber insisted they were getting in character, Johnny's not so sure, especially with James' reputation as a skirtchaser."

The two stars are seen with their arms around each other while filming some scenes in New York City together, and looked quite comfortable with one another. "And while it was just for the cameras, James looked quite pleased to be cuddled up next to the beautiful star," Daily Mail reports.

The 36-year-old hunk was snapped wearing a blacked leather jacket over grey T-shirt, black jeans and a pair of leather boots, while wearing his signature scruff on his face. Dressing down with black leather biker jacket and light denim jeans, Heard looks at ease in the arms of the actor as they both carried hot beverages while walking on the sidewalk.

Looking like a hipster couple, the duo's latest snap fueled a lot of speculations that their closeness goes beyond the movie. Although the two may looked like they are just having a good time, "the film's subject matter is much more serious in tone as it details a man's search for his identity while investigating a notorious 2007 San Francisco murder trial about a computer programmer who kills his Russian wife, whom he met through an online dating service."

Penned for James by Pamela Romanowsky, the multi-talented actor acquired the rights to Stephen Elliot's memoir "The Adderall Diaries" in September 2010 which now stars Ed Harris, Christian Slater and Cynthia Nixon.

Amber and Johnny was last seen together during the Aerosmith's concert at the Xfinity Center in Mansfield, Mass., where Depp jammed with the band. The 51-year-old Casanova grabbed a guitar and played "Train Kept a Rollin" with the legendary band in front of its screaming fans and his fiancée.