Teeny Weeny or the Splat Monster, formerly known as Teeny Weeny Ninjalino and Tiny Ninjalino, was Night Ninja's former spy, An Yu's current Mystery Mountain Guardian assistant, and he is the deuteragonist of the PJ Masks.
In "The Splat Monster", he transformed into the Splat Monster when he touched the transforming splat in the cave of Mystery Mountain. By the end of the episode, An Yu turned him back to his normal form. Eventually in "A Teeny Weeny Problem", An Yu decided to give him back the transforming splat in order to promote him to become the Mystery Mountain Guardian assistant.
Like the Ninjalinos, he is shown to be quite fast and agile. But he is hardly shown using other weapons such as "Sticky Splats" until "Armadylan Zen".
In his Splat Monster form, he has super strength and can also shoot red sticky splats, which he can telepathically control. Teeny Weeny can only access this form when he sneezes while holding the Mystery Mountain ritual scroll that leads to a cave containing transformation splat.
Unlike the other Ninjalinos, Teeny Weeny will be shown to be less obedient with Night Ninja at certain circumstances and will sometimes side with the PJ Masks. It is also emphasized in "Catboy and the Teeny Weeny Ninjalino" that Teeny Weeny is afraid, can get lost easily at places and is shown to not understand some phrases and sentences that people say, although he can speak English properly like the other Ninjalinos.
However, since his appearance on Season 3, he starts to become more obedient and fully complies to Night Ninja's orders. As of that, he stopped siding with the PJ Masks for now. This lasted until the events of "The Splat Monster", "Clash on Mystery Mountain" and "A Teeny Weeny Problem" where he decided to turn on his master once more.
When Teeny Weeny transforms into The Splat Monster, he becomes much more defiant to Night Ninja's orders and often becomes enraged and attacks Night Ninja and his fellow Ninjalinos. However, he is still friendly to An Yu and the PJ Masks when in this form.
Teeny Weeny is identical to the Ninjalinos, except he is smaller in size, and very cute.
In his Splat Monster/Gigantus form, he's made of red sticky splats and has a muscular body, but the Teeny Weeny Ninjalino's face can still be seen. In this form, he is once more disobedient towards Night Ninja, and won't hesitate to attack him.