It features a pet that is interactive and can talk with the user. The iPet is also user-designable or can be downloaded off of the Internet from other iPet users.
If you want to make your own pet, then open up the "MyPet" file in ResEdit, and simply replace the pictures and text with appropriate images, and then save it. You can send any pets you make to email@example.com and they will include them with future versions of iPet.
There are just a couple of things to note while using iPet. There is still a bug with memory usage when speaking: Sometimes the program will crash after it has been speaking for a long time. Increasing the amount of memory for the program will help with this problem.