No Joke! Bitter Feud Explodes Between Comedians Jimmy Fallon & James Corden

James Corden has become famous for his cozy routines with celebrities from Jennifer Lopez to Julia Roberts, but behind all the fun and laughter the popular comedian is a focused man with a plan — and he has Jimmy Fallon in his sights!

"He sees Jimmy as a loose cannon and it's just a matter of time before he screws up."

As RadarOnline.com reported in October, Fallon's drinking is reportedly so out of control that executives have become concerned.

"There were fears that Fallon was out of control and something could happen while he's out drinking," one NBC insider told Page Six . "Things got so serious at one stage that execs feared that Jimmy was splitting up with his wife over his drinking, but they patched things up."

"They couldn't be more polar opposites — James lives a sober life off-camera and is careful about not partying with his staff."

Meanwhile, continued the source, "Jimmy has no such boundaries and loves to tie one on with his crew ."

And that could leave the door open for the focused Corden to make the ultimate move.

"James has every intention of knocking Fallon off his pedestal when the time is right and he's playing a slow and studied game to make it happen," the insider explained.

"James studies Jimmy's program to make sure they haven't copied his funniest bits, while Jimmy tends to crash James' interviews at events."