It's ... right there in the title. Ultra-curator Master0fHyrule, whose last video compared all the final smashes of Super Smash Bros. 3DS to Smash Bros. Brawl, is back at it to deliver every idle animation for the 251 Pokémon comprising the series' first two generations.
The animations come from Pokémon Stadium 2, where if the player does nothing and does it long enough, their Pokémon does a battle pose, followed by their battle cry. The Pokémon Stadium series on Nintendo 64 introduced the battle cries and rendered the Pokémon bestiary in 3D.
Previous works of Master0fHyrule include a compilation of idle animations in numerous Nintendo games, and more than 100 ways for Link to die in The Legend of Zelda: Majora's Mask.