Fishketball is a parody of the game titled basketball. It is also a portmanteau (a word that is composed of sounds from two different words) of fish and basketball.
During the lunch scene, Oona's tail appears red. But she's really wearing red baseball pants.
This is the only episode where nothing bad happens to Gil during the intermissions. The worst that happens to him is getting hit in the face by a meatball.
The guppies go outside twice in this episode.
When this episode was being created at Nick Digital, there was a scene in which Molly helped one of the Little Fish play bubble ball. It was deleted, but it is currently being shown as an interstitial on Nick Jr. They'd hopefully put on it as deleted footage on a Bubble Guppies DVD.
In the game, it seems you don't play against another team.