When playing on Polus Replica, there are passive mini crewmate items you can pick up. The level up description for each says "Allegedly offers better moral support."
Does upgrading the mini crewmate items do anything?
It has effect!
According to the fandom pages of those crewmates, (and playing with the Mini Ghost). They imitate a weapon/item: first level of Mini Ghost is the same as first level of the Lancet. 2nd is the same as level 2 Lancet, 3rd the same as level 3 lancet.
That's why the are referred on the pages as 'lesser' versions. They are funny but for me personally always have a low upgrade priority.