Quick question about battle portraits

[-Champ-]

When i was watching a stream the other day, i noticed that every now and then one of the players battle portraits (specifically sheik) would get a "sparkle" on it for a second. What is this, and what does it do?

 

[Game&Watcher]

I think it has to do with completely charging chargeable specials.

 

[Cha Cha San]

Idk if it's what you mean but when you KO somebody, your portrait will have a little flame showing you got it.

 

[Blablabug]

Flame when you KO, Sparkle when you charged something (it applies for , maybe for too but I'm not sure).