- They're found mostly in people's houses. 
- They come out mainly at night. 
- They run around like little wind-up toys. 
- They have two speeds: stop and fast. 
- They naturally avoid people. 
- If you try to grab them they dive into the nearest tiny hole. 
- Once they've hidden they can be extremely difficult to find. 
- They seem to like living in what basically amounts to a pile of trash. 
- They eat little bits of food, crumbs, etc. 
- They tend to be brown. 
- They reproduce very rapidly. 
- Fear of them (and similar creatures) is not terribly uncommon. 

Conclusion: hamsters are large cockroaches