Idk about the name. I guess that frogs inflate in cartoons but it's a bit silly. However, the mechanic is solid. It's like Oran-Rief or its ruins.

The only problem I can see is that there's no downside beside tapping a creature. Maybe add a mana cost to it. Or tap down the target. What would be perfect is if you had to put a -1/-1 counter on THIS creature when you did it. Thats quite black, +1 counters are green. Perfect synergy. ALSO, it means that if you inflate a creature for a bunch, then you can inflate other creatures later and the -1 counters just remove his ones.

@Izaac The downside is that you lose a blocker for a turn for only a little upside and if you're using the ability over and over again your opponents get to get in a pile of damage. A mana cost could work, but then the mechanic might be too weak for limited.

Tapping the target could work.

I don't like putting a -1/-1 counter on this creature, the ability can also go on non-creature things so it wouldn't work to have the ability in reminder text. Also having -1/-1 counters and +1/+1 counters in the same set can get confusing.

It only works on creatures that entered the battlefield this turn, so there's no way you could get rid of the -1/-1 counters with Inflate later.

The creatures having to enter the battlefield this turn makes this mechanic fair but it also makes this mechanic feel like a green blue mechanic a lot more than a green black one, which coincidentally suits frogs XD.