I Have a player who is always talking about running a different game and if we would play.
I FUCKING hate when people bring up running other games when I have spent hours preparing to run one for this group. If you want to fucking run a game, go do it. Just don't bring it up when we are playing MY game.
Also backseat DMing, HOLY FUCK it grinds my gears. Don't ad-lib, don't tell the other players what happens, don't tell me that something should be acrobatics check and not athletics just because you have proficiency in Dex. Fucking stop playing songs on your phone to "add atmosphere" when half the time its fucking JRPG shit. Just shut the fuck up and play the game, Michael.