Like that exact example, the shadow transformation does come out due to extreme anger, while partial shadow transformations can be actively controlled!
However, while the other forms can be fully toggled, they do have their set parameters that cause them to automatically activate:
The Incubus form can automatically occur due to extreme lust
The Ghost form automatically toggles in October, cause of Halloween
"The Creature" can automatically toggle in April for April Fool's, but it can be forced to stay off
... all other "forms" tho have to be manually toggled, along with "combination" forms like "Ghostly Werewolf", "Shadow Umbreon", etc etc
