Nessie is a sea monster who lives in the lake in Penguin Village. It is based on the Lock Ness monster.
Nessie makes its first appearance in Dr. Slump in the "Penguin Gran Prix" chapters. During the race, Arale Norimaki temporarily stops running to play with the monster.
The Adventures of Tongpoo
Nessie makes a brief appearance in Akira Toriyama's later manga The Adventures of Tongpoo, when the Sun rises in the morning.
Dragon Ball Z
In Dragon Ball Z: Battle of Gods, a pink monster who looks similar to Nessie lives in the lake that surrounds Beerus' Castle.
Oishii Shima no Ū-sama
In the manga Oishii Shima no Ū-sama, a sea monster similar to Nessie lives in a lake on Guruguru island.