Small pokemon sprites!? Could there be large ones too!?

With there being so many pikachu spawns yesterday it was easy to see that some were smaller or larger by comparison. I saw this as a bug of some sort until my other half said she assumed it was due to the appraisal. Did anyone catch two side by side that were small and large and see what the appraisals said? We've always wondered if size mattered (insert that's what she said joke) but does size matter in how we see pokemon now?