Meet Tickle and Pickle, the Guinea Pigs of our classroom.  When we got these Guinea Pigs there was no way we could have known they'd be as amazing as they turned out to be in our class. When the children have the opportunity to hold them they gain a sense of respect for other living creatures. We sit closely with them to make sure they and the Guineas are save but allow them to discover the Guineas as much on their own as possible. They are able to feed them carrots, lettuce, and apples which sparks many conversations about healthy food in our class. 
One of my favorite things about these Guineas being in the room is the children who are timid of them at first. It's amazing to watch their growth around them to where they'll finially pat/hold them.