Has anyone else seen this?

That is the animation indicating a gym is under attack. Remote feeding a gym that is under attack for some reason causes the animation to follow you home.

You are about to gain super powers

Help! It's coming to get me!

I had it happen a while ago. Dont remember the circumstances though. It was visually awesome, like being in a lightning tornado.

You're about to learn ultra instinct
[Dragon Ball Super humor]

Heard it had something to do with gym battles.

I found one too :)