When SpongeBob shows Patrick the technique to blow bubbles, SpongeBob's first example is blowing three duck bubbles that eventually float away.
A duck bubble parent and its three children are seen playing in the park as a bubble family watches them.
"Who R Zoo?"
It is one of the many animals SpongeBob and Patrick create for their Bubble Zoo. It and the rest of the bubble zoo animals later destroy the zoo and break out of it to terrorize Bikini Bottom because Squidward disturbed them.