I was just wondering, I've seen some correlatives change form like other nouns and adjectives, so do all the correlatives follow the same pattern that nouns and adjectives do?

You can add a plural ending J to the correlatives with the endings A and U.

You can add an accusative ending N to the correlatives with the endings A, O, U and - to express direction - E.

According to a Lingva Respondo by Zamenhof, there is no grammatical rule that prohibits something like ioj, but the sense of these correlatives usually does not allow this.