When my daughter was ~3, we would use her pop-up fire engine tent as our spaceship, then hop out onto a planet after landing and pick some random stuffed animal

When my daughter was ~3, we would use her pop-up fire engine tent as our spaceship, then hop out onto a planet after landing and pick some random stuffed animals to represent aliens. "pickle planet puppy" was a favorite recurring character. lots of earthquakes and volcanoes to create urgency to get back to the ship. Little kids' imaginations are powerful!