If you're looking for some unique ways to celebrate Pokémon's 20th anniversary, how about mixing the catch 'em all franchise with Mobile Suit Gundam? That's exactly what one fan did, and you can see the process involved in making Gundam models themed after Charizard, Blastoise, and Venusaur over at their image gallery.
As for the finished product, the the full finalized gallery is here, with highlights below followed by info on what models and parts were used for each kit.
HG Danazine for the base
HG Al-Saachez's Aeu Enact for arms and tail "fins"
HG Dom R35 for base
HG (revive) Qubeley for shoulders and backskirt and funnels
HG Kshatriya for funnels only
HG Gusion for the base
Gunpla Builders Parts "MS Cannon 01"