I'm honestly curious how the artist went about making this.

Fat, spherical appearance: Magnezone, Magmortar, Drifblim, Dusknoir, Spiritomb.
Navy blue and black colors: Garchomp, Rampardos, Luxray, Empoleon, Toxicroak, Probopass, Lucario.
Stubby arms and legs ending in claws: Torterra, Lickilicky, Rhyperior, Magmortar, Electivire, Heatran.
Short spikes: Giratina, Garchomp, Rampardos, Bastiodon, Torterra.
Beady yellow eyes: Gliscor, Purugly, Bastiodon, Infernape, Garchomp.
Big chompy mouth: Drapion, Heatran, Carnivine, Spiritomb, Bastiodon.
Floats in the air: Drifblim, Chingling, Bronzong, the Lake Trio, Manaphy, Giratina, Vespiqueen, Rotom, Probopass.