S2·E17 Top of the Sky

Sally, Nick and Cat are playing with their toy rocket. Using the Cat's Whoa-Look-At-It-Go-Launcher then he shoots the rocket up to the sky. But now they need to go find it. Off to the top of the sky, they pass the treetops and the mountains. He answered "where is the top of the sky?". They meet a treehopper and a yak until they keep going higher until they're in space. They meet Audrey the Astronaut who explains that there is no top to the sky. The sky turns into space and space goes on forever. Just when the kids think their rocket is lost, they find it in Audrey's space station. Although they can't launch their rocket to the top of the sky, launching it to the moon is just as cool.