This image comes from a recent Huffington Post article that talks about the short film. (You can check it out at this link.) I love the use of the couple of whales, this might be Uku is singing about everyone having someone to "lava". You can also see the whales in the first thing we saw of the film, the poster along with other animals that are in "lava".
This is getting me thinking if we will see the other animals from the poster or that the animals will help Uku find "lava". Those were just guesses but we will find out what happens in Uku when the short debuts to everyone on June 19th along with Inside Out. And also I still can't get the song from the clip out of my head.