They appear in New Super Mario Bros: The Underground as one-hit enemys. They can squirt ink at the player, which makes them very slippery.
A single Scoot Bloop appears in Lets-a-go, Mario as the second mini-boss of the Beach Area. This one cannot be stomped, and instead, must be peppered with fireballs, eighty of them to be exact. However, Scoot Bloop will scuttle around the room at about the speed of a Flurry. It will then jump, freeze somewhere in the air, and spew ink all over the room. This must be dodged by swimming. He can also attempt to spear the player. If he hits the ceiling when he does this, several rocks will fall.
Rocket Rick makes this boss exceptionally because he can repeatedly charge into Scoot Bloop, stunning it in the process.