Voltorb. This mysterious Pokémon uses strong Electric attacks, and is often found near power plants. Use extreme caution; Voltorb may explode without warning.
– Ash’s Pokedex
Voltorb looks like a Pokeball. When it evolves into Electrode, its colours are inverted. Voltorb tends to explode of self destruct, maybe that’s why it looks angry all the time, probably has pent-up anger inside it, causing it to explode. I often think that Voltorb (and Electrode) should be part Steel, because their appearance in the anime or 3D games makes it look like a metallic ball.
Stat-wise, Voltorb is fast. With 100 base Speed, it’s faster than many fully-evolved Pokemon. Strangely, before Gen II, Voltorb didn’t learn any Electric moves by level-up.