i want mac to have a recurring background boyfriend for like at least 3 episodes and then there's an ep where he's really excited to introduce his first bf to the rest of the gang via an embarrassingly formal dinner. but he and dennis end up in a huge fight when dennis -- even more irritatable than usual -- blows up and storms out of the restaurant after the bf is a few minutes late. (why should he bother meeting the guy when he obviously doesn't give a real fuck about mac?)
the bf arrives shortly after, extremely apologetic. he's good-looking and charming, with just enough rough edges to fit in. he wins dee, charlie, and frank over quickly; makes mac almost forget about the fight with dennis. they all have a great time together. get tipsy. hit a bar. dance and drink even more.
at some point, mac and the bf have an intimate, startlingly serious conversation about what had happened with dennis earlier. about mac's feelings for dennis and their fucked-up history. about mac and the bf's feelings for each other and their possible future??? they kiss with emotion.
mac laughs to himself a little afterwards and confides that dennis has been such an asshole lately that he's been secretly using just for men touch of grey when he dyes dennis' hair. instantly, dennis peels off his hyper-realistic silicone mask and launches into a bond villain monologue about how he suspected mac was sabotaging him so he fabricated this identity and pretended to be mac's bf until he could trick mac into feeling safe enough to reveal his secret.
dee and charlie say that mac has been bragging about switching out dennis' hair dye almost every day at the bar, and they could have told him if he'd asked ever.
"dude you like full-on fucked me multiple times," mac says.
"no," dennis says. "you're not understanding."
hard cut to the gang back at paddy's later. everything is normal.