I decided

Alex is an interdimensional traveling shapeshifter and he always has to fit in with the creatures in the dimensions he visits so he just collects forms to always have something to wear until he's accustomed to a new one that fits better into the dimension he's in.

So sometimes he's just a random duck or dog or something until he learned enough to become a good member of a species, to not stick out too much and just learn and travel around the areas