Back at the beginning of the modern LGBT umbrella, gays were given the stereotype of all being hookup obsessed kinky motorcycle enthusiasts, the 'leather daddy and boi' look. It's good to look tough when protesting for your right to exist.

Around the 90s the jazzercise fit athletic picky eater gay became a trope on television - your classic twink.

The problem with both those poster boy stereotypes is they're both positioned as kinda in-your-face and combative, so gays that just wanted to live life emerged - fat, unthreatening, and likely to invite you to their BBQ - the modern bear.

Meanwhile, the internet is just becoming a thing and in the early days 'nobody on the internet knows if you're a dog' as the expression goes. Without a corporal body as reference, people are reduced to their chosen name/handle, their profile pic and whatever thoughts they posted. Internet culture filled the gaps with anime girls and cats - creating the perfect culture for mascot suiting to evolve into a new niche.

Finally, pup play stems from the biker boi kink of gimp play (sensory deprivation), someone stitched leather ears onto a gimp hood to reduce a (consensual adult) person to 'just an obedient animal' with the original look meant to dehumanize and anonymize. Ironically this play has gone through radical transformations and softened as most modern pup hoods are colorful expressions of individuality. Today pup play is a great sampler platter of kinks and adult activities in general (including many that are family friendly). It's a great way for stressed adults to step away from adulting for an evening and just play.

Also, don't take my description as fully gospel, all of these movements are complicated with regional variations, and since these are generally voluntary labels and useful stereotypes, you'll find plenty of people who see these differently or wish to gatekeep, etc. So take this all with grains of salt