Joe Dirt -- I'm Back ... And Taking Selfies

"Joe Dirt" and his glorious mullet are back ... and David Spade took a selfie to prove his classic 'do will be front and center for the new flick.

You may recall ... the 2001 film ended with Dirt's mullet being replaced with dreadlocks -- but it looks like that's all changed for the new movie set to debut next year on Crackle.

Spade captioned the pic, "Day 1. Let's get this s*** started! #imjoedirt #whatscrappenin."

Home is where you make it.