At the beginning of your end step, Prairie Dog’s triggered ability will check to see if you’ve cast a spell from your hand this turn. If you have, the ability won’t trigger at all. If the ability does trigger, it will check again as it tries to resolve. If you’ve cast a spell from your hand since the ability triggered, the ability won’t do anything.

If a creature you control would enter the battlefield with a number of +1/+1 counters on it on a turn where Prairie Dog’s last ability has resolved once, it enters with that many plus one instead.

If two or more effects attempt to modify how many counters would be put onto a permanent you control, you choose the order to apply those effects, no matter who controls the sources of those effects.

You can activate Prairie Dog’s last ability multiple times in a single turn. If it resolves twice, the number of +1/+1 counters put on a creature you control is two plus the original number. Three activations and resolutions add three, and so on.