Madness

Madness is a slang term given to cards that can put creatures into your battle zone instead when they are discarded from your hand.

Details
There are 2 types of these "Madness" abilities.

During your opponents turn:
 * This first appeared in DM-06 Stomp-A-Trons of Invincible Wrath with cards such as Dava Torey, Seeker of Clouds.

They are worded as

It appeared on popular cards such as Terradragon Arque Delacerna, Baiken, Blue Dragon of the Hidden Blade and Sanfist, the Savage Vizier. It also features on the Admiral archetype of creatures who each feature this ability.

While they can only be put into the battle zone during your opponents turn with their abilities, they can be used if one of your cards such as Emergency Typhoon or Hundred Eyes, Secret Spirit Treasure discards it from your hand with its Shield Trigger ability.


 * Psychen Pippi and Super Psychen Pippi is also seen as similar to this type of ability, but with putting a different creature (Gaial Kaiser) into the battle zone instead.

By opponents cards: This type of madness ability appeared in DMR-02 Episode 1: Dark Side with Eternal Meteor Kaiser.

Unlike the "During your opponents turn" cards, you can't use your own cards to summon these creatures as only your opponents abilities or spells can trigger them.

However, breaking a shield such as Locomotiver or Ghost Touch as a Shield Trigger will allow you to use that ability to put a creature out if they would be discarded.

Currently, they can only be triggered by your opponents creatures or spells, so Cross Gears or Fortresses such as Master Weapon - All Yes or XENOM, the Reaper Fortress don't trigger them.

Alien Father and Mother Alien are similar in how they are triggered by your opponents cards, but are put into the mana zone, not the battle zone.

Trivia

 * It is named after the keyword from Magic: The Gathering.