Amp

Amps, also known as Electro-Chomps in the New Super Mario Bros. Wii strategy guide, are small, electrified metal balls who have appeared as enemies throughout the Mario series.

Super Mario 64/Super Mario 64 DS
They are featured in several levels of Super Mario 64 and its remake Super Mario 64 DS. Similar to Li'l Sparkys and Hotheads, they move around objects and platforms and if Mario comes into contact with one, he will be shocked and lose one wedge of health.

New Super Mario Bros.
Amps reappear as an uncommon enemy in New Super Mario Bros., in several Tower levels. In this game, they appear mostly in groups, and if Mario comes in contact with one, he will be shocked. They can only be defeated with a Mega Mushroom, Blue Shell, or Starman.

Super Mario Galaxy
Amps can also be found in many areas of Super Mario Galaxy, including the Buoy Base Galaxy, the Battlerock Galaxy, and the Dreadnought Galaxy. They have faces, just like in the other games, but some of them are larger and do not have a face. Despite of that, they will still act the same way as in the other games, and they will move as well.

New Super Mario Bros. Wii
Amps also appear in New Super Mario Bros. Wii, behaving the same way it did in New Super Mario Bros. They can be defeated by getting frozen by the Ice Flower then being ground pounded on, touched by a character using a Starman, or by having a frozen enemy thrown at them.

Super Mario Galaxy 2
Amps reappear in Super Mario Galaxy 2, behaving the same way they did in the prequel.

Mario Party series
They appear in various games in the Mario Party series. In Mario Party 4, the Sparky Sticker was made as a sticker of an amp. They were renamed Zaps for the next Mario Party games.

A Zap Orb appeared in Mario Party 6 and Mario Party 7.

They also appeared in Mario Party 5, but they were referred to by the traditional name of "Amps".

An Amp also appeared in the Mario Party 8 mini-game Spector Inspector.

A single Amp appeared in Mario Party Advance. There, it appears as a citizen of Town Area and needs help in winning a game in Town Game Room B. Notably, it sometimes uses electric terms in its speech. Also, Amps appear in various mini-games as enemies.

Appearance and Traits
Amps originally sported white "cross-popping" veins, joyful red eyes, and rounded metallic lips with a pure red mouth. Since Super Mario 64 DS and Mario Party 7, their appearance has been changed a bit. They now have more jagged yellow eyes and a larger, jagged mouth. Their lips are now white, with a pink tongue and black interior being visible inside the mouth. They are also now black rather than grayish and sport no angry veins.

Trivia

 * Their name stems from "ampere" (often shortened to "amp"), the standard unit of measurement for the speed of electrical currents.
 * There are only two Amps that chase Mario in Super Mario 64, both found inside the pyramid of Shifting Sand Land. However, these Amps do not appear in the DS remake.