thdhted:
Mind if I gave my own input?
Muddy Goomy: It is odd it doesn't learn Surf, but I suppose there is some logic. The Goomy family is a slug/snail (yes it's part Dragon but design and flavor wise they more focus on its slug/snail origin, actually they insult its dragon part) which would explain at least why it gets Muddy Water. But why not Surf? Well maybe because it isn't part Water-type. The other two non-Water-type that learns Muddy Water (and Surf) is Stunfisk (who's is based on a fish) and Lickitung (who's a Normal-type so naturally learns a lot of elemental moves; it also only learns it through breeding). And the other slug Pokemon, Shellos & Gastrodon, are part Water-type. So I think its a combination of it being a slug/snail and also not being part Water-type.
Curldavoir: Well first off it only got it as a Tutor Move in Emerald. Also Ralts and Kirlia get it and I don't think they'll have a problem doing it (and even if they made it so Gardevoir didn't learn it it'll still get it could still get it when it was a Ralts/Kirlia). But as for how does Gardevoir itself curl without hurting itself? Well who says those horns are hard? Maybe they're soft or at least can bend. The spikes are a psychic manifestation of Gardevoir's heart so maybe it can turn it back into energy or recall them into its body. Or maybe it just curls up in a way that it isn't poking itself. Also curling up doesn't mean it turns into a ball, it could maybe duck and cover.
Egg Peck: Many animals who hatch from eggs have something called an "
egg tooth". It's a hard tip at the end of a beak (like for birds and turtles) or snout (crocodiles) that the baby uses to break their way out of the egg. Since Togepi is based on an animal hatching from an egg (and it becoming more avian as it evolves), it makes sense. As for what it uses? Well it could have an actual tooth, or being the "Spike Ball" Pokemon maybe it uses one of its spike.
More Togepi: For Dream Eater maybe its a joke on how when you have a baby its crying keeps you up thus sapping your strength. :P Pluck could just be an extension of the "egg tooth" idea, and finally Present because it just likes you that much (Togepi and its evolution are sort of manifestations of happiness an joy).
Gen II Pay Day: Though it's not immediately obvious, the Hoppip family does have a slight resemble to a cat (most obvious with Hoppip). Pay Day's Japanese name is "Coin for a cat". However since Hoppip is more based on a weed they decided to remove it though it was later given to Purloin since it's a sneaky cat like Meowth.
Spiderchu: Pikachu creates an electricified net (note in its description it says its a net) that looks like a web rather then electrically charged silk.
This also goes for the other Electric-types that learn it (and Porygon).
Mewtwo Logic: Mewtwo doesn't need to Surf as it can levitate itself over the water. However to go underwater it does need to Dive (probably surrounding itself with Psychic energy).
Plant Teeth: Victreebel has teeth.
Do you maybe mean its pre-evolution, Weepinbell?
Since Bellsprout can't learn Bug Bite but Victreebel can, maybe Weepinbell have developing teeth we just don't see? It could also be a reference/joke that it's not biting like a bug but rather it eats bugs since its based on a pitcher plant (which could explain some of the other non-Bug-types that learn it too ;)).
Quiet Like The Night: First, Umbreon doesn't learn Miracle Eye. Two, it gets it as an Egg Move, as in EEVEE gets it. It's not meant for Umbreon, its meant for the other Eeveelutions who can use it (though why I don't know; they may have raised its Power to 120 though they still need to re-think that move (like at least have it do typeless or maybe even direct damage thus getting around the whole type chart problem)).
Loud Sleeper: Snore just says the Pokemon makes a loud sound while sleeping, don't need a mouth to do that.
