In Osomatsu-san: Tamashii no Takoyaki Party to Densetsu no Otomari-kai, the story begins with the sextuplets prepping for a takoyaki-cooking party at their home, before everything goes haywire when Totoko implies a sleepover. 

(Source: Anime News Network, edited)
 

Note: To commemorate the 6th anniversary of Osomatsu-san anime, two new animation projects that will have a theatrical release were announced at the "Fes Matsu-san '21" event, with one in 2022, and the other the following year.