#133 -- Eevee - Normal
#753 --lv@Wind Rock->
Galeon - Flying
This is essentially blasphemy, or as close as it gets, since I'm probably the number one person to try talking people out of making eeveelutions that don't make sense.
Because the concept behind Eevee is that it is a perfectly normal pet-like pokemon,
which upon exposure to a pure source of elemental energy undergoes a complete transformation, essentially fully gaining said elemental abilities.
That's what Eevee has always been about. And that's why I still stand at calling "Bullshit" whenever I see people make ones for silly types (especially Bug, Ghost, Dragon). I mean, what's it gonna be exposed to; a beetle rock, feel the aura of insectness and turn into a different kind of animal? Go and make a new pokemon that evolves into different species then, Eevee was never meant to do that.
The other types could be argued about (Ground/Rock/Steel, Fight/Poison), but my main counterargument is that these don't have that certain elemental feel, they're too much about physical stuff/minerals and startegy/technique.
So how the heck did I get to Flying?
Obviously anyone sticking wings on an Eevee and changing its colour is just as silly as any of the above.
It's Normal/Flying by all means in that case.
If a freaking balloon and a dragon with clouds for wings don't justify being true Flying pokemon, then a winged rodent doesn't even remotely.
One really core element has always been Wind. But there is no Wind type in Pokémon. For a good reason though. There simply isn't much you can do with it that wouldn't just as well fit into a few other types. There's things like Leaf Tornado and Leaf Storm, which would obviously stay Grass even if Wind existed as a type. Same if there was Sandstorm-esque moves etc. It's more of a side-effect or an extra. Just like light could be an attribute of Electric or even Fire (And Flash is Normal, with the only Pokémon learning it being a Bug type, Volbeat..), making it a type doesn't make sense with how types are set up.
But moves that incorporate wind, but have zero relation with any actual type, the move does usually end up with being Flying, but even here you have exceptions like Whirlwind and Razor Wind where Normal seems to work just fine.
Thinking about all this, making an eeveelution whose look would not scream "Normal/Flying!" seemed like a big challenge. The result is Galeon.
Cloud-like cushions are constantly generated underneath its feet, the one forming around its neck assures it stays head up, while its ears help it keep balance easily. So it's essentially full-time airborne. Even when it takes a nap.