What’s the deal with banner pets?

[a small animal]

I did not know about banner pets or whatever anyone was talking about until I clicked on the trick or treat sign and got a pet. Are they rare? I see that a lot of people have them so I’m not sure if they really are hard to get. The designs are very cool though, I love the fennec.

[Juliamon]

They are only available during events that have those clickable banners, and are fairly uncommon (I only got one of each kind this time, but in past events I've gotten multiples). Since they're not all available at once the ones released later in the event tend to be rarer: last year had four banner pets, and the first three are uncommon and the last one is rare.