Megawhatts (a play on the words megawatt and what) are mischievous little creatures composed of electrical energy who have the physical form of anthropomorphized batteries. They come from the Nosedeen Quasar.
They are black and yellow with plus and minus symbols on their back, similar to a battery, and a lightning bolt on their chest. The top of their heads constantly emit electricity. They stand roughly a foot high, have pointy legs (though they usually fly), and have only three fingers on each hand. Their language consists of a series of high-pitched squeaking and chirping noises, though they are apparently capable of understanding English. But Ben's version of a Megawhatt (Buzzshock) is very different. It sports a pretty much all black body, with a big white lightning bolt-like stripe running down from it's neck to it's belly. The omnitrix icon lays on its stomach and its electricity is green instead of yellow.
Megawhatts can control electricity and can inhabit electrical devices, controlling them from the inside. Being made from electrical energy, they are weak against things that ground it (water being a chief example). They grow stronger by absorbing electricity and can multiply if split in half or given enough power. It should be noted that that when the first one divided, both it and its clone seemed to be surprised, as if they didn't know they were capable of doing it. It should also be noted that Megawhatts are surprisingly strong for their size, as just one was able to lift Grandpa Max, who is many times its size, into the air by his underwear and giving him a flying wedgie. Another notable ability of theirs is that the noises they normally use to communicate can, at a certain pitch and volume, shatter glass.
Megawhatts exist to have "fun", which in their case is to cause trouble wherever they go. While they cause a lot of damage, Megawhatts do not seem to technically be evil, and in fact are not openly hostile to humans, merely lacking any self-control or sense of the harm they may be causing. They only openly attack after Ben tries to attack them, and don't retaliate against anyone but him.
They are said to be either lightning come to life, static cling run amuck, or an alien (the first two were said by the town leader and the last by Gwen, which is correct).
Ben 10,000's use of a Megawhatt as a form on the Omnitrix. Ben's son, Ken, also gets Buzzshock (Megawhatt) as a beginning alien, except that Ben and Ken can speak while in this form, as Ben can with Benmummy when the original seemed to be mute. However, as the Omnitrix can absorb and integrate DNA for use by the wearer, they could still have originated on Earth.
They appeared in the episode "Tourist Trap", originally trapped in the world's biggest rubber-band ball. Ben's use of the Omnitrix accidentally empowers them enough to escape their rubber prison. They are currently imprisoned within the world's largest lightbulb, which was originally the world's largest fishbowl adapted into a makeshift prison. The mayor of Sparksville has it converted into a lightbulb to replace the lost attraction.