Sore Ike! Anpanman: Tetsu no Hoshi no Iron Christmas

Today is the long-awaited Christmas Eve! An Iron Christmas party is being held on Iron Planet. Kokin-chan is having a blast since it's her first time on Iron Planet. She makes friends with Kotetsu-chan and they play together at the Iron amusement park. But then the Iron's precious Christmas tree gets transformed into Baikinman's robot! Everyone is turned into a tree, and they're in big trouble. They all have to protect their precious Christmas before Santa arrives!

(Source: Amazon, translated)