Cody Garbrandt says Demetrious Johnson better ice up ... 'cause he's coming for the UFC legend right after he smashes through T.J. Dillashaw

Cody and TJ are set to square off at UFC 213 in July -- it will be Cody's first fight since winning the UFC bantamweight championship back in December. The two hate each other's guts and are coaching opposite each other on "The Ultimate Fighter 25" which premiers tonight on FS1. 

But after they square off in the Octagon, Cody tells TMZ Sports he wants Mighty Mouse -- and says meeting DJ at the 125 pounds won't be a problem.

And who would be the favorite in that fight? Cody's got some thoughts on that.