If you want to have fun in a normals game and just mess around with your 3-4 man premade

#LET THE OTHER TEAM MEMBERS WHO ARE NOT IN IT KNOW

I have no issues with having fun and just goofing around in a normals game. But you need to let your teammates know ahead of time so they are not trying to salvage a win which unbeknownst to them, is not possible because you are not playing, or even wanting, to win by any means. Its just common courtesy.