Octoballs are small, round Octarians with one large eye and a pair of purple lips. Because of their body shape, they are able to roll on smooth surfaces while leaving behind a thick trail of purple ink. When shot with Inkling ink, they are pushed backwards but not harmed. However, if submerged in a puddle of Agent 3's ink, they will struggle to move and can be destroyed.
A total of nine Octoballs can be found in Splat-Switch Revolution. Three of them are located in Checkpoint 1, while six of them are located in Checkpoint 4.
Several are spawned in Enter the Octobot King! where they are spawned in the fourth section of the battle.
Splatoon 2
For unknown reasons, Octoballs do not return in Splatoon 2 and have no representation whatsoever.
Octo Expansion
Despite not appearing in the main game, sanitized versions do make an appearance in the Octo Expansion, though never used as enemies, with them being trapped in storage units during the Belly Phase as well as inside the liquid lasers of the NILS Statue. When the NILS is destroyed, these Octoballs can be seen flying out. It is unknown why they do not appear as regular enemies.
At the end of the fan-made issue of Splatoon, Specs, (an Inkling from Team Blue), flies over a group of Octotroopers and Octoballs. It is most likely that they would not appear in the manga again, but will possibly do so due to the Inkopolis Tower not having the Great Zapfish on it.
Tips
Octoballs can be easily defeated by letting them swim in Agent 3's turf, in which the animation of the Octoball will look like it is trying to escape the ink. When that animation plays, Agent 3 can easily splat the Octoball.
Trivia
Despite Cap'n Cuttlefish saying they must be submerged, Octoballs can also be defeated by knocking them out-of-bounds. This is useful for the Inkling Girl amiibo levels, as they can be sniped off the cliffs while in their own ink.
Despite not appearing in Octo Canyon, concept art of a bowling alley stage that features them prominently can be seen in The Art of Splatoon 2.[1]
In Splatoon 3's single-player campaign Return of the Mammalians, there is an enemy named the Octodisco. It looks very similar to the Octoball but Octodiscos can fly and look like a disco ball.