I think this'd be a great idea. But only if they were creatu-themed.
I also think it'd be a good idea to add the matching ears.
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SPONTANEOUS IDEA
Okay, so we all know how failed seasonal pets get special items?
Well, maybe failed regular pets could get that tails/ears, and the seasonals get their items + the tails/ears.
This would up the price of so-called "COMMON" eggs, further up seasonals, and make colours more valuable.
Another thing for the tail/ears is that the ratio of the colour rarity would match the tails. Nattie being the most common, then sepia, etc.