A young boy is walking along the shore, searching for bottle tops, when he finds a large, red, metallic object—it has tentacles! It resembles an octopus trapped inside a diving helmet. He greets it, and suddenly it springs to life. Equipped with two big pincers at the front, this creature simply wants to have fun and build sandcastles with its new human companion. As evening arrives, the boy notices that his friend doesn't have anywhere to live. It has no family, no acquaintances—absolutely nothing! He asks a scientifically-minded acquaintance to help him figure out what his metal friend is, but they ultimately decide it’s simply lost and he will just need to bring it home to his parents, regardless of the mess. Then he spots an advertisement on television for the "Federal Dept. for Odds and Ends." That became his idea—they must know something about it! Perhaps they would have been able to assist him if he hadn't gotten bogged down in paperwork and bureaucratic procedures, and then discouraged by a cleaning person. It seems like the best possibility is that it will eventually recall where it needs to be on its own. So, let’s try that approach... Tim Minchin’s quiet narration really elevates this charming puzzle, and as the pair spend the day looking for places "thing" could live, the creators are given complete freedom to invent a variety of bright and imaginative situations using different animation styles to populate this straightforward story with numerous creatures—human and otherwise. I did find it enjoyable, even though it ends on a somewhat melancholy note.

Source on TMDB