Shout out to @Toolstony , @KniteBlargh , @G8Crasher , @KatimuX @Was-_PandaxXnowKay being the first to confirm they found one! (give me photo evidence in the comments and I'll add you as well)

What are the odds of finding a shiny sticker?

When they are active, it is 1 out of 5.

How can I know when one's active?

You don't, that's the fun of it. Shiny stickers will show up more or less at random when I feel like it; and be available for about 24 hours, or until someone finds one!

How do you choose which sticker is shiny?

Roll of the dice. The sticker currently shiny will be chosen at complete random.

Why?

I thought it'd be kinda fun tbh. Stickers are basically collectors items anyways, so having special editions I thought would be really cool, especially if they were rare.

I'm a creator too, and would like to do something similar, can I?

Sure! Go ahead, and lemme know so I can try my hand at picking up one of your shinnies! ^.^

You don't need to credit me for the idea since it's fairly generic, but you can if you want.

I saw these stickers are fanmade, could mine be one?

Yes, of course! The contest for Wave II is going until April 21st. You can find more details here.