Mr. Osomatsu the Movie: Prologue Theater
Osomatsu-san The Movie: Maesetsu Gekijou · えいがのおそ松さん前説劇場
Synopsis
Prologue shorts included with the BD/DVD release of Mr. Osomatsu The Movie. A single short was screened in theaters per how many weeks the movie was playing, with each acting as a prologue to the movie.
Source: MANGA