We own a guinea pig.  Visitors have called her a hamster, a gerbil, and a rat.  I don't think she's been offended by this as she appears to have the idea that she might be a cat.

She sits in her cage by herself just kind of "pigging around", rooting through shavings and snuffling at things.  Every so often she appears to want company so we take her out where she settles down, gets patted and talked to, eats her treats and then drops herself off the couch.  I don't think depth perception is a strong point with her. 

On the floor, she'll eat the odd newspaper, cat toy, book, bit of clothing, carpet and, lately, cat food out of the cat's dish.  She roots around for a couple hours, doing pig things and then it's time for her to go back.  And the chase begins.  My partner chases her under the couch, into the bathroom, where she invariably eludes capture, out into the livingroom, underthe loveseat, back into the kitchen, and she finally parks herself under the couch where she started.  This causes much huffing and puffing and furniture moving, ending up in a very frustrated, "Stupid pig.  I don't know what her issue is.  I can't catch her."  At which point, I smile sweetly at him "It's ok - I'll get her this time."  I then go to the fridge, get out a cucumber, cut some bits off and coax her out, pick her up and pop her back into the cage.  It's a nightly game of ours and provides hours of entertainment.  I highly recommend it to any coulples who feel that excitement is lacking in the relationship.