Only select areas in which Scaler journeys allow him to transform into these creatures, and only one of this five forms are usable in these locations. By feeding Reppy Klokkies, she secretes a gaseous ooze that give Scaler some useful upgrades.
Scaler can only access certain transformations in specific regions, and only one of the five options is applicable in those locations. When Reppy Klokkies is fed to her, she secretes a useful gas that improves Scaler's capabilities.