Cozy Yarn is a B-grade Pet. It is considered the best B-grade (and possibly overall non-S-rank) pet in the game, due to its ability to produce Bonus Time Jellies (known as the best type of Power Jelly) reliably. It is one of two Pets capable of producing Bonus Time Jellies, the other being Magic Pod, which produces a Bonus Time Blast Jelly. Players lacking S-grade Pets can use Cozy Yarn to aid in both coin farming and scoring.
This pet was once very popular in Seasons 1 & 2, because of the fact that you could get bonus points without the loss of energy. Although its usage has decreased among experienced players, it is still a very good scoring Pet for beginner players.
When descending in Bonus Time, its "tail" curls into a heart shape.