The rule could be anything, as funny or as serious as you want. The universe will progress in a similar way that it has up until this point, unless your changed rule prevented it from doing so.
Some examples might be:
- The invention of currency is not allowed.
- Iron is slightly less stable.
- The Ancient Greeks are able to cultivate Silphium, which does not go extinct now.
maybe it would look like a reverse snowfall underwater if the ice is buoyant? I imagine if the ice stayed at the bottom it would be interesting evolution wise since most things survive the cold by being at the bottom.
Is it your cake day? What’s the cake next to your name mean?
If so, happy cake day!