Mongoose, mongeese, and mongi.

Personally, I prefer mongi. But people sometimes make a stink about grammatically incorrect phrases, but frankly, I don't really care. And mongeese is incorrect to! (Who knew, right?) But iv'e lived perfectly fine saying mongi or mongeese. Seriously, it's not that big of a deal.

-Written By my twelve year old son

                                   Disclaimer: He does not have a mustache