From Sonic Retro
|Game: Sonic Unleashed|
|Affiliation: Eggman Empire|
Thunder Balls wander around, ignoring Sonic in most cases. They do, however, discharge electricity from their bodies, making them hazardous to attack or even touch. In the Xbox 360/PlayStation 3 version, Thunder Balls appear only in the nighttime stages, specifically Dragon Road Act 1, Arid Sands Act 1 and Eggmanland. If they spot Sonic, they will follow his trail, albeit slowly. When they're not discharging electricity, Sonic can pick them up and toss them into a body of water to electrocute any enemies making contact with the water.
In the Wii/PlayStation 2 version, they appear only in the daytime stages, specifically Cool Edge, Dragon Road and Arid Sands where they behave very much like the Thunder Spinners, hovering in place and discharging electricity.
|“||These critters hover along, emitting high-voltage bursts periodically. If they spot Sonic, they'll make a bee-line for him.
Not even their designer is 100% sure how they float like that.!
— Encyclopedia, 360/PS3 version