On Friday, M wanted to drink some water out of one of the little medicine dosing cups that is including with children's liquid medicine. I gave him one and he took it into the bathroom to get some water. I heard a bunch of slurping and sucking, finally got annoyed and told him that was enough water and to bring me the cup.
He emerged with his mouth looking like this. Evidentially all of the sucking and slurping I heard was him creating suction to stick the cup around his lips. He's been walking around all weekend with a self-given hickey. I've been fighting the urge (sometimes successfully, sometimes not) to refer to him as "hickey-lips".