He wants to dress like B, talk like B, hang out in "Daddy's shop" and build furniture, ride the John Deere lawnmower ("Daddy's tractor") and generally engage in tiny testosterone-building activities. The era of Mama is over.
I have found a way to capitalize on this, though, by coming up with utterly ridiculous nicknames and having Mac repeat them just to prove he's Daddy's bugaboo/handsome boy/chunk-chunk*, not Mama's. (Excuse the grainy, about-to-die camera footage.)
To add insult to injury, Mac now responds to my "I love you" with "Yeah." I'm working on that, with mixed results. (I've warned B not to respond like that, either. Not good for a girl's ego, y'all!)
*To be fair, I called Mac "fat-fat" and "chunk-chunk" when he was in the 3rd weight percentile at nine months old. These days he tips the scales at 37 pounds, so it's a more accurate description - but it has always been a term of endearment. And it just sounds so cute coming out of his mouth!