There is actually a lot of convincing evidence as to why Pearl might in fact be White Diamond:
- A pearl isn't actually a stone, it's the calcified organic byproduct of molluscs. As the Gems talk about Steven being unique due to his organic nature, Pearl can't be a pearl. The only explanation is that she is a different stone, disguised as a pearl.
- Pearl's features resemble the hard lines of a diamond more than the soft curves of a pearl. Her hair tapers to a point. Her head can be seen as a diamond shape. Her nose is a diamond. If she puts her legs together and holds her hands together above her head, her body makes a perfect diamond. Can this possibly be coincidence?
- Pearl never shapeshifts. Shapeshifting would reveal that she is in fact a diamond.
- Pearl's spacesuit has a diamond on it, betraying her diamond nature.
- In 'Maximum Capacity', Pearl's cardigan is covered in diamonds, teasing us as to her true form.
- Pearl's spear is sharp, almost diamond-like!
- Jasper realises that Pearl is not a real pearl, calling her a 'defective pearl'. But she is unable to realise Pearl's true nature as a diamond.
- In 'Sworn to the Sword', Pearl sings about not being made to fight. No, she was made to rule, as a diamond.
- Pearl is the master of lies. In 'So Many Birthdays' she declares her love of pie, and yet bare episodes later in 'Fusion Cuisine' she makes a fuss about how she hates to eat any food. What else is Pearl lying about?
- Pearl seems very upset about Rose's death. This is strange. Perhaps Pearl is upset that she didn't get to kill Rose herself?
- In 'Serious Steven', the characters enter a giant white diamond pyramid. Pearl is oddly reluctant to use her genius tactical nature to figure the pyramid out - could it be that she didn't want the other Gems to learn its secrets and deactivate it?
- In 'The Return', Peridot's laser deliberately swerves to avoid Pearl when it's heading straight for her. Why could this be? Perhaps Pearl is Peridot's secret master?
- Why does Pearl seem so interested in the Gem fragments in 'Secret Team'. Could she want to be using them for the same purpose as Peridot was in 'Keeping It Together'?
Could Pearl have infiltrated Rose's resistance group for evil purposes? Could she have set Rose's group against Homeworld in an attempt to cause a civil war that she would be the final victor of?
Can it be any coincidence that Pearl attempted to flee Earth just as Lapis made it off-planet? Was Pearl planning on rejoining her Diamond Authority cronies for the final war on Earth?