Background colors...

[EmeraldSky]

This may sound stupid, but...

Why are there cool swirly backgrounds when a character summons a Pokemon and/or battles?

 

[misty_moon]

For effect my friend. xD plus, that's what they do on anime things

 

[jynx]

So the background won't be too boring

 

[kohei]

I guess 'cause it looks nice and it's really cool and stuff...... yeah.......

 

[Sean Fury]

Why are there cool swirly backgrounds when a character summons a Pokemon and/or battles?

To illustrate the illusion of a large creature escaping from a tiny, vortex-like prison circle that we call a Pokeball.

Or, because they're bright and shiny and people like to stare at bright and shiny.

You decide.