Unfortunately for Puck, Loki was the 'younger' brother. Granted, Thor had usually held back (which Loki was called by and grateful for both). But it meant a tickle-wrestling match was something he was used to. "Sorry, my Robin. I've experience with this game." But Loki laughed anyways, and was glad for the play-fighting. Even rewarding Puck with a kiss or two to his cheeks, or hair, or an ear.