Goldfish
From Tardis Wiki, the free Doctor Who reference
Goldfish were a species of fish native to Earth, they were renowned for their short memory. The Doctor stated he wasn't a goldfish when it was suggested he had forgotten the events of a mere moment ago. (DW: The Romans) In Cardiff as part of Torchwood Three, Suzie Costello bought goldfish in bulk and began killing them to test the Resurrection gauntlet. (TW: Everything Changes)
