nazono mito
The animegao kigurumi version of Nijisanji's Tsukino Mito, revealed on her 2019 April Fools stream. Later nicknamed Nazono Mito (lit. Mysterious Rabbit) by fans, the mysterious figure appeared in full Tsukino Mito cosplay (including an animegao mask and zentai bodysuit).
The stream and the bizarre character were very popular among fans to the point that Nazono Mito is treated as a recurring character in Tsukino Mito's channel.