It's a bit of a tricky one because "foolish" is already an adjective, and adjectives don't have past participles in the same way verbs do.
Here's why it's confusing:
* Verb: The verb form is "to fool." The past participle of "to fool" is "fooled."
* Adjective: The adjective form is "foolish." It describes a state or quality, not an action.
So, while you can say "I was fooled," you wouldn't say "I was foolish-ed."