From the Amazon River, I think they should ALL have this pet:
The Candiru:

If I could afford it, I would pay even double, for trips to the amazon for the DUmmies, so long as they included large doses of swimming naked in the amazon - a stipulation which we all know they would see as a bonus. And, the Candiru being parasitic in nature, it and the DUmmies would bond closely and immediately, and not just in the physical sense. It could be the best action PHDD has ever had too...

For those of you who may not know about this fish, you may not want to.
Not for the faint hearted rofl.(On edit: Don't they already have a pet walrus shared collectively?)
CMD