New 'Vacation' Movie -- It's the Griswolds!

No, it's not Chevy Chase and Beverly D'Angelo ... Ed Helms and Christina Applegate are taking over the Griswold family reigns for the next "Vacation" flick -- and filming has FINALLY started.

Helms plays a grown up version of Rusty Griswold -- originally played by Anthony Michael Hall -- and the plot centers around Ed taking his wife (Applegate) and their kids to Wally World.

The storyline may sound familiar ... but there are rumblings Chase and D'Angelo will reprise their famous roles in the flick ... so it should be pretty fun.

So much fun you'll be whistling Zip-a-Dee-Doo-Dah ... well, you know the rest.