The fake evolution of Popplio is a brilliant compromise in design.
- Popplio is yet another marine mammal. There's already been several with Seel/Dewgong, Spheal/Sealeo/Walreign, and Oshawott/Dewott/Samurott. So right off the bat you need to differentiate it enough from those existing Pokemon. Maybe you don't choose a sea lion or a walrus, but instead something like an elephant seal.
- Popplio is cute and friendly-looking. It isn't exactly neutral or indifferent as designs go, it actually has a some pep. One might see it as a critical elemental to keep throughout evolution stages to keep a happy go-lucky smile.
- Popplio has a small and sleek shape, like a real seal. Compare it with the chubby and dopey looking Oshawott, Popllio has got a closer real-world resemblance. You can't bulk it up too much otherwise it destroys the qualities of the first stage. If you're a fast starter from birth, chances are you'll be a fast starter all grown up.
- The clown motif may or may not have some huge significance, but how much it should be relied upon comes down to the original intent of the designers. It's clear Venusaur wanted to have a giant plant on his back but would you guessed that Charizard would have wings or Blastoise would have cannons? How much style versus how much substance is anyone's guess at this point.
- The clumsy Typing vulnerabilities on the website mean that folks were scoping out a -Fighting look for the evolution. The majority of those Pokemon are bipedal, so how does one get a flippered mammal to resemble a fighter without straying too far from the original concept? The fake probably got the closest. I'd say, if the Types hold true, we'll see something similar in the official reveal.
In other words, that's how you end up with an Insane Clown Posse Strong Man Upright Seal.