Illustration: Philippe Poirier
The mesmerism token is placed on the staff member as a way to test that they can be mesmerised. For example, Android Greeter and Pod Person cannot have tokens placed on them by the Mesmerist ability, so the mesmerism fails. Because the first part of the sentence fails, you ignore the remainder of the sentence, and cannot make the chosen staff member available or unavailable.
The presence of the token then prevents repeat mesmerism. The token is not removed at the end of the round - it stays in place indefinitely.
Being mesmerised to make a staff member available again doesn't reset that staff member's ability; if it is only allowed to be used once per round, and it has already used once that round, it's too late.
Previously "Once per Events step: Choose a staff member without a mesmerism token in any park. Add a mesmerism token and move them to your park until the Cleanup step."
Previously "Once per Events step: You may choose a staff member in any park who has no mesmerism tokens. That staff member gains a mesmerism token and you get exclusive use of their abilities this round."
Even after being revised once, this guy's effect raised many questions. The fundamental problem is that control of a card is normally based on having that card in your park, and the Mesmerist tried to give control of the ability to another player, for use at their discretion at a later time, without actually giving the card to them.
The current revision provides a new ability not currently available anywhere else: to make a staff member available again once they have been made unavailable. Because it's an immediate change in state, there are no questions raised about ongoing control, such as what happens if someone steals or dismisses the Mesmerist.