[Velocity]

Originally Posted by Foxamivalth

Weezing (♀)
Ability: Levitate
Obtain: Trade with paperfairy
Sig Move: Poison Storm

Spoiler:

Weezing releases his gas to the arena. The gas rages each round and allows Weezing to grow another head.

As BW Dex says, a triplet can be found as Weezing feed on enough gas.
Type: Poison | BP: - | Accuracy: 100
Classification: Status/Weather
Target: Entire Field
Energy Modifier: 7
Effects: Weather. At the end of every round for 2 rounds except the last, each active Pokémon, except Poison types, loses 4 HP simultaneously. Damage dealt by Poison-type attacks is multiplied by 1.5. Damage dealt by Poison (PSN) and Toxic (TXC) effect are raised by 2. At the end of this weather effect, Weezing has 30% chance to grow 1 more head. By getting 1 more head, Weezing gains Atk and Sp.Atk by 1 stage (Atk + 1, Sp.Atk + 1).
Usage Gap: Once per 2 Rounds

I really wish you'd start putting more description into these things...

Either way, the one 'every round for two rounds except the last' is quite confusing and I have no idea what part of the effect it refers to. Also, you should probably specify that only one extra head can be grown.
Pend'ng.