In pairs or small groups players silently become non-human objects together
learn to pay attention to each other and work together
enforce non-verbal "yes and"
diagnose strong lead vs. follow tendencies
You can start with section 1 or jump right into section 2.
Section 1: Have everyone walk around the room, and tell them that you'll call out a number and they need to form groups of that number as quickly as possible. For instance, they are walking and you call out, "three!" Then they need to form groups of three [plan ahead by figuring out how big the group is and what numbers they can easily divide into; you may have to say "groups of three or four" if the math doesn't work out].
Then tell them that you'll call out a number and also an object that they need to collectively become. For instance, "groups of three! Strawberry!" They need to form groups of three and become one strawberry. It's helpful to alternate between organic and inorganic things (the ocean, a skyscraper, and so on). It's also fun to form groups of one and the whole group.
Section 2: At this point, you can get a group of 7 or so up and the rest watches. Tell them you'll give them an object to create collectively. Encourage them to do it in silence and as quickly as possible. After a few different objects, get another group up.
1) It's great to encourage the group in section 2 to look at each other with anticipation as they receive the suggestion. That way, the group can move together and really create the object collectively.
2) With some objects, you can encourage them to move around (e.g. as a cat or dog) or activate (e.g. as a lamp or toaster).
3) In a debrief, it's helpful to identify that leadership in this context means making an offer, making a first proposal. It doesn't mean bossing other people around.
4) It's also helpful to point out that if you don't know what to become, just join someone else in what they're doing! This is a great lesson of improv: don't try too hard to get it right, just join!
5) Can be helpful to have people walk around to 'reset' their group shape so the same people don't end up in the same locations within the objects.
With emotions: In both sections, you can encourage the players to choose or discover an emotion when they form their object. And they can do so collectively or individually. It's helpful to clarify which option they should be working on at any given time.
Break apart: Once the object is established, the object can break apart and each person can explore what it's like to move through space as their part of the object and then come back together again. This works well if they have sounds and emotions established. As they are broken apart, their emotion and sound can crescendo, so that when they come back together again, they are a much higher energy version of the object.