I think I just figured out what you were talking about and why I could not duplicate it. If you were referring to the floating balloons and other glitter that was appearing on all messages — that has already disappeared. It was a short term iOS 10.3 promotional gimmick that lasted only a few days and then self destructed. It should be long gone from your iPhone by now.
Yes that was it exactly. And it does seem to be gone now. That's a relief.
