Weekly Shōnen Jump, the magazine in which Sket Dance runs, makes frequent cameos throughout the manga and anime. This is an ongoing comprehensive list of those sightings. If you see a Weekly Jump somewhere in the series, add it in! Thus far, the magazine has been spotted in the following places:
Seen in Bossun's hands while Himeko is practicing guitar.
The Sket Dan can be seen reading an edition of the magazine with Gintoki's face on it at the beginning of the chapter and before Gintoki and his pals appear.
After the credits, the book is seen in Bossun's hands.
Seen on the train billboard in Dante's flashback.
Seen in Jōgasaki's hands.
Seen on a bookshelf in the Sket Dan's clubroom.
Near the beginning, Bossun can be seen reading it until Himeko shows her special ability.