The Glitterball (1977)

When a group of small aliens accidentally abandons one of their own on Earth, adventurous kids Max and Pete stumble upon the "Glitterball" and attempt to return it to its mother ship. As the children learn more about the friendly alien and its magical powers, they must protect their new companion from an army corporal and a small-time thief who are both hunting the extraterrestrial for their own cruel purposes.