The latest MTG Arena update implemented the new Mastery system, and a new cosmetic cat to join us on the battlefield as part of its purchase. You can interact with your cat and change its color, and your opponent can also see the changes as well.
A few days ago, a player reported that it is possible to exploit the system by “spam” clicking on your cat to lag your opponent.
Wizards are encouraging players to report any players purposely spam clicking the cat, roping or stalling. Players are reporting being suspended from the game for five days (regardless of intent or awareness of issue) as a consequence.
Wizards are working on a fix for this issue to go live in next week’s update, but in the meantime you can disable emotes in the settings to block out this function.