Ox
bee
A bee and an ass.
EE wordsfleegleeLL wordsballbellbillcallcelldilldolldullfallfellfillfullgillgullhallhillhullmallmillmulltelltalltillwallwellwillyellNN wordsbannSS wordsbassbossfusslasslesslossmassmessmissmossmussTT wordsbattbuttmittmuttwatt
It's a Parakeet! ^^
"Double letters" means two in a row, like tt in "letter" or oo, kk, and ee in "bookkeeper".
a and l
deer
hippopotamus
animals and animals
ai, ox
Ox