This is the third time all the current villains appear (except for Motsuki).
However, in spite of Motsuki's absence, this is also the first time all the current villains and An Yu made cameos.
This is the fifth time PJ Masks ended on a cliffhanger. At the end of the episode, after the PJ Masks chant their victory catchphrase, the Teleporting Crystal can be seen sinking to the bottom of the moat. Afterwards, a large, blue-greenish tentacle appears, snatching the crystal from its place.
The only other character with a feature like this is the infamously leaked upcoming villain of Season 4, Octobella. So it is likely that the tentacle is foreshadowing her.
As a result, Octobella may use the aforementioned crystal for her advantage, presumably to teleport to wherever she wants to go.
This and "Moon Madness" also foreshadow the future events of Season 4, since Luna Girl said in one scene at the beginning of the episode that she'll get her Moon Crystal back, regarding the events of the latter.
Gekko is called "Lil' Green" for the first time, but not by a villain. Instead, he is called this by Catboy after Night Ninja (who referred to Gekko as Catboy's little green friend) told him that he'll get him (Gekko) for getting rid of Night Ninja's catapult.