What it says in the title. If you step on Wavey Jones's head, then eat something to bring your sanity above the threshold, he'll still reappear in a few seconds.
1. Spawn Wavey Jones.
2. Raise sanity above 75% and step on his head. (Either order has the same result.)
3. Wavey reappears a few seconds later and will continue doing so until the end of the night, regardless of sanity.