Okay I am going to be open minded here, and I don't know much about rats so please tell me why someone would even consider having one as a pet?
The rat's living space is where he spends the majority of his time. In the wild, rats spend much of their time foraging for food and building nests. Activities, such as running, jumping, climbing, digging, and gnawing, are also important occupations for domestic rats, although most live in cages. An enriched cage environment should provide the necessary space and arrangement to support the rat's normal activities. For example, rats are "edge-users"; they like to stay close to walls and huddle into tight places. But rats also need to have room to stretch and stand upright on their hind legs.