Ship's cat
Mrs. Chippy was the ship's cat aboard Endurance, the ship used by Sir Ernest Shackleton for his Imperial Trans-Antarctic Expedition.  (The Expedition's goal was to cross the Antarctic by land.)  After about a month, the crew realized that "Mrs. Chippy" was actually a male cat.  However, by then, everyone was used to the name "Mrs. Chippy," and kept using it.