Kyutai Panic Adventure!

Both are crossovers between two or more different anime with short episode. While Kyutai Panic Adventure is shounen-centered (One Piece/Dragon Ball/Astro Boy), Magica Quartet x Nisioisin is a collaboration between Mahou Shoujo Madoka Magica and Nisemonogatari. 

Both are crossovers between two or more different anime with short episode. While Kyutai Panic Adventure is shounen-centered (One Piece/Dragon Ball/Astro Boy), Mahou Shoujo Sonico Magica is more like a parody on Mahou Shoujo Madoka Magica in Super Sonico style. 

Both are short crossovers between lot of anime. While Kyutai Panic Adventure is shonen centered (Dragon Ball, One Piece, Astro Boy), CLAMP in Wonderland is simply mashup of lots of anime made by CLAMP (RG Veda, Tsubasa Chronicle, Magic Knight Rayearth...). Both have old style animation.