The Blastoids are very small Badniks resembling grenades. They have a silver body with a pair of wide eyes, footstools, and an antenna that creates a spark line between it and the Blastoids' upper point.
The Blastoids are only found in Carnival Night Zone, where they usually appear in small groups within open corridors, and can hang from the ceilings or stand on the floor, remaining stationary. Some also come in pairs. After a set amount of time (usually around three seconds), the Blastoids will teleport from one side of the tunnel to the other, emitting four electrical charges as they do so in a forty-five degree angle as well as emitting a lightning pulse while teleporting.
The player has to move carefully when crossing the Blastoid's path. As long as they are not traveling or emitting sparks, the Sparkles can be defeated by being jumped on, or by using the Spin Dash. A Lightning Shield will protect the user from all of the Blastoid's electricity, but not from physical contact with them.
These robots appear to be waterproof.
- In a Sonic The Comic Q Zone which covered Sonic the Hedgehog 3, the Blastoid is referred to as "Blaster". This is actually the name of a separate Badnik that was mistakenly left in the original manual after its zone was moved to Sonic & Knuckles relatively late in development.