Sad, Sad Santa is the 50th chapter of the Dr. Slump manga.
Summary
It is Christmas Eve. Senbei Norimaki, disguised as Santa Claus, gives his autograph to the residents of Penguin Village: Arale Norimaki, Akane Kimidori, King Nikochan, Kurikinton Soramame, Kinoko Sarada, and Midori Yamabuki. The next morning, Midori is angry at him for entering her apartment.