This episode article is in need of a synopsis. A synopsis is intended to be a very detailed description of what occurs in the episode.
Share with others and don't be selfish.
A place is for sharing.
This is the third time that Night Ninja works with the PJ Masks, but it happened later, since they acted neutral and attempted to give advice to Night Ninja and the Wolfy Kids on sharing Mystery Mountain.
In one scene, Night Ninja mentions the Mystery Mountain Scroll from "Race Up Mystery Mountain" that the PJ Masks never got back from. This references the PJs' first-ever failure from Mystery Mountain's debut episode, though the PJs themselves no longer worry about the scroll in the entire TV series, and the museum presumably has a fake duplicate of it on display.
The Wolfy Kids become the second villains to be at Mystery Mountain.