The "Watermelon Stevens" are characters who appear in "Watermelon Steven" and are the episode's main antagonists.
The Watermelon Stevens are Steven-shaped humanoid watermelons. They have bumps on their heads resembling Steven's hair and are close to Steven's height. They each have two black watermelon seeds for eyes and dark and medium green stripes running vertically down their bodies.
Steven is seen spitting watermelon seeds outside of It's A Wash, without knowing he inherited Rose Quartz's chlorokinesis ability. Steven's saliva cause the discarded seeds to develop into fully-formed sentient watermelons by the next day.
Rose's plants acted as her guardians, and similarly the Watermelon Stevens defend Steven from harm. Though initially docile, the Watermelon Stevens become increasingly aggressive towards "threats" to Steven, regardless Steven's commands and the lack of any real danger. Due to his lack of control over the new power, Steven cannot prevent the Watermelons Stevens' rampage. This inspires Baby Melon to sacrifice himself by punching Steven, diverting the Watermelon Steven's attention away from the Crystal Gems who they were previously attacking. Upset, Steven tells them to go and not come back until they understand Baby Melon's sacrifice, and they comply. It is unknown if they will reappear; they were last seen going deep into the ocean and being picked up by seagulls.
The Watermelon Stevens protect Steven when he is faced with any potential danger.
Ronaldo buys a Watermelon Steven and decides to perform an autopsy of it for the website Weirdstar. Realizing that they are alive, Steven tries to stop Ronaldo. Ronaldo hits Steven with a spatula, and the Watermelon Stevens act to protect Steven.
- When angry, the Watermelon Stevens are revealed to have mouths.
- They are the first antagonists to protect Steven.