From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Four Monarchs (スパイス の 男の子, Supaisu no Otokonoko; FUNimation "Spice Boys") are four aliens who replace Garlic Jr.'s original crew of Ginger, Nikki, and Sansho. They are under the command of Garlic Jr. during the Garlic Jr. Saga. They are strong, brave, evil, and totally devoted to Garlic Jr. Their names are derived from condiments: Tard, Vinegar, Zald, and Gasshu. The commander is Gasshu, a white-haired alien and the most handsome of the four. Zald is a short and stubby red alien with a Mongolian-type hat. Both Tard and Vinegar are large, brawny, muscled aliens.
At the beginning of the Garlic Jr. Saga, Salt and Mustard killed a few innocent people. They also attacked Gohan, and Salt and Mustard held Piccolo in place to allow the vampires (under the control of the Black Water Mist) to bite him. Spice was the only one of the four who seemed to know that anyone bitten by someone infected by the Black Water Mist would become just like them. When Gohan and Krillin arrived at Kami's Lookout, Salt and Mustard fought Krillin and Gohan, beating them up. Salt nearly killed Krillin with an energy blast which forced Gohan to unleash his hidden powers, killing both Salt and Mustard with a Masenko blast. After Piccolo revealed that he was only pretending to be affected by the Black Water Mist, Gohan and Krillin fought Spice and Vinegar and seemed evenly matched. Gohan defeated Spice and Vinegar, seriously injuring them both. (Spice being impaled on a spike.) Afterwards, Spice and Vinegar were powered up and healed by Planet Makyo, beefing them up. They began to pummel Gohan and Kuririn, and Vinegar nearly killed Kuririn. Out of rage, Gohan killed both Spice and Vinegar simultaneously in midair, unleashing his hidden powers once again.
They are named the Demonic Four Monarchs in the Dragon Book.
They are named the Shiten'nō Mazoku (四天王 の 魔族; Literally meaning "Four Heavenly Kings of the Demon Clan") in Dragon Ball: Daizenshū 7.
- The four members of the Four Monarchs have the same height as the four members of the Ginyu Special Corps: Zald is Ghurd's height, Tard is Butta's height, Vinegar is Recoome's height, and Gasshu is Jheese's height.
- All of the Four Monarchs meet their ends at the hands of Gohan. They are also the first villains Gohan destroys.