The reason Puck needed Hannah's body is that he was somehow unable to land in his Kill-T-Gang form.
Hanna confronts him, and tells Captain Earth that he would cause a "Libido Burst" if he did it that way, and that is the reason he needed her body.
But the other Planetary Gears Kill-T-Gangs had no such concerns.
The Type-1 Kill-T-Gang caused one such libido burst on the moon. What was different with Puck?
