One day, Nobita finds a stray dog drowning in a river while playing by the river side. Feeling sorry for the dog, he decides to take it home by hiding it in a "kennel on the wall" and names it Ichi (originated from "One", which sounds similar to "wan", the sound a dog makes according to the Japanese language), and secretly feeds it and plays with Ichi with his Kendama to find. Soon after, he also adopts a stray cat named Zubu (or wet in Japanese, due to the discovery of it in a rainstorm)... and many other stray cats…
Source: MAL