This enemy appears to be four Doges carrying a large birthday cake that stands on a can of Cat Food. At the top of the cake there is a red and gold colored ribbon and a sign written in gold that says Happy Birthday. The Doges remain hidden under the can but can be seen during its attack animation. Although it may not look like one, it is actually a Metal enemy.
Cow Cat and any other fast attacking characters such as Mr. can kill this enemy very easily. It deals pretty much no damage per hit, so there's no need to worry about it at all.