Can we talk about #PetPhotosFriday? I don't get why it's so huge all of a sudden.

I started seeing #PetPhotosFriday all over my social media a few weeks back. It's just people posting pictures of their pets (which is cute, don't get me wrong). But why did this one hashtag blow up when there are already tons like #CatsOfInstagram or #Doggo? I mean, I posted my cat Whiskers with it and got way more likes than usual (weird, right?). Is it the catchy name that makes it stick? Or maybe people just love a scheduled thing to look forward to. What do you all think makes a hashtag take off like that?