Paradox Brothers

Para and Dox, the Paradox Brothers, are two twin brothers who work for Pegasus in the Duelist Kingdom arc of Yu-Gi-Oh!

The Anime
The Paradox Brothers are two of Pegasus's eliminators who like to rhyme with each other. Para is wearing orange and Dox is wearing green, and each has a different symbol on his forehead. Dox also speaks in a lower-pitched voice than Para. They duel their opponents in an underground labyrinth in a tag team duel, in which if one loses, then they both lose. Their most powerful monster is Gate Guardian, the fusion of Suijin, Sanga, and Kazaejin. They dueled Yugi and Joey, and lost when both their life points went to zero as Gate Guardian was destroyed by Black Skull Dragon, a fusion of Yugi's Summoned Skull and Joey's Red Eyes Black Dragon.

However, they told Yugi to choose a door, between Para's door and Dox's door. One led to the exit next to Pegasus's castle, and the other led to an endless maze of darkness and despair. Yugi marked two coins each with Para or Dox's symbol and told them the coin clenched in his fist is his choice. He revealed Dox's coin, indicating that he chose Para's door. However, the Paradox Brothers, able to choose which door leads to which path, made it Dox's door, but in reality, Yugi expected this - the coin clenched in his fist was for Dox's door, and the one he revealed had Para's symbol on the other side, and so Yugi and the gang escaped the labyrinth.

The Paradox Brothers are never seen following this, except as lost souls in Season 4, Waking the Dragons, alongside Panik, Bandit Keith, Seeker, Arkana, and Yami Marik. As they have never (to the extent of our knowledge) been killed, trapped in the Shadow Realm, or taken by the Orichalcos, it is likely they and the others were just an illusion.

In the Japanese version, the final credits scene shows them dueling Mai Valentine and Vivian Wong on the Great Wall of China.