You can put various kinds of "poison pill" in the shareholder rights agreements which are binding contracts on both the company and its shareholders in response to events.

You can also make all sort of post acquisition agreements.

These usually take the form of making stock available at steep discounts in response to actions e.g. in the event of a 20% layoff any employee from the time of acquisition can purchase stock at $0.10 a share, any one laid off will get a million dollars severance, if acquirer shuts down the studio the original founders have the right to re-acquire all IP and trademarks for $1 -- those sorts of things.

This isn't a specific kind of entity, any business entity can have Shareholder Rights Agreements. It's a bit of a game to get the terms right so everything is in good faith and agreeable.