...unlikely at my house, but if you're even considering it, be sure to check out Home-to-Home, the ALL LOCAL pet adoption alternative.
According to Pet Place, the best pets for children under age six are guinea pigs, hamsters, gerbils, rats (what?), small birds (they recommend budgies), and fish.
A budgie, by the way, is a type of parakeet.
Turns out that rats are very sociable, love to play and can even be trained. There are hairless rats, dumbo rats, miniature rats, not to mention blue, platinum or sparkly silver rats. If you get a fancy rat, you may even win ribbons at the next rat show... But keep it down, rats like company but not chaos.
Reptiles don't make the list for young kids because they carry salmonella (I would like to add that corn snakes can live up to 20 years--that's a long commitment). Rabbits are described as temperamental.
In grade school, my niece was raising hamsters to sell (after George turned out to be Georgina, there was nothing else to be done). Sadly (for the hamsters) her best customer became her little brother, who saved 25 cents off the cost of a mouse from the pet store to feed to his corn snake. Ah, capitalism.