Whether you consider a lizard or any type of species to be a pet or a pest is totally up to you and your personal preferences. Mice are a good example. Some people keep mice as pets, but most people consider mice to be a pest. In the case of lizards, the colourful iguanas are often seen as a pet. The small, tiny house lizards that come into your home uninvited and can cause health hazards, can be seen as a pest.