Overview
Similar to Madoka Titus, The meme is originated from Futaba Channel's Inner Model board (模型裏板, mokei uraban).
While Madoka Titus is a collaboration formed using Gundam AGE-1 Titus parts to combine with Madoka figma/Nendroid, Homura Sparrow is formed using parts from Gundam AGE-1 Sparrow to combine with Homura figma/Nendroid.
There are also people using parts from Gafran to combine with Homura. But that's another matter whole together...