you were helping Danno around the Bonelab story mode and he just got the body log item a couple levels ago which is the item players need to switch character appearance during certain scenarios in the different levels. so after the magma gate level it was now time for the moon base level

Danno: looking very excited for the moon base level and he was still carrying you with one hand

Then, his body log activated causing him to transform into a short humanoid cat version of himself