O
O'Malley
O'Mally
O'Neil
O'Roy
O-Ren Ishii (after the character in the Kill Bill movie)
O.B.
O.B. (Orange Boy
O.C. (Ordinary Cat)
O.C. (Other Cat)
O.F.C. (Our First Cat)
O.J.
O.J. Simpson
O.N.N.A.O. (Oh No, Not Another One)
O.T.M.
Oaf
Oakes
Oakichobi
Oakii
Oakley
Oakley Lucifer Fila Nike Levi Reebok
Oasis
Oatcake
Oatmeal
Oats
Obelix
Oberon
Oberon Casimir Badpaintjob
Oberon The Wonder Gut (Lord of the Faery Cats)
Oberon-Smiley
Obi
Obi Wan Kenobi
Obie (O.B.)
Obijuan
Obo
Obsidian
Obsididan
Obstinate
Ocabar
Occi
Occupant
Ocelot
Oci Osborne
Ocitar
Octavia
October
Odan
Odd
Oddball
Oddibe
Oddly McStrange
Odeipus
Odessa
Odette
Odie
Odile
Odin (Viking mythology the allmighty god)
Odo
Odyssey
Oedipus
Ofel
Ofelia
Off!
Off-License
Often
Og
Ogden
Ogies (Afrikaans for Little eyes)
Ogopogo
Oh Arrogant One
Oh Captain My Captain
Oh Oh
Oh-lee
Oi!
Oingo
Oink
Okavango
Okee
Okesha
Oki
Okie
Okinawa
Oklahoma
Okra
Oksana
Ol Yeller
Ol' Buddy
Ol' Sport
Olaf
Old D
Old Deuteronomy
Old Grandad
Old School
Old Sweetie
Old Yeller
Olde Scratch
Oleg
Oleo
Olga
Olhausen
Olia
Olimpia
Olive
Oliver
Oliver Sebastian
Oliver Stone
Oliver Twister
Olivette
Olivia
Olivia Pawdancer
Olivia The Otter Cat
Olivier Serpentine
Olja
Olla
Ollendorff
Olli
Ollie
Ollie Bollie Mc Follie
Ollie North
Ollie South
Olliecat
Oloff
Olsen.
Oly
Olympia DuKatKis
Olympician
Olympus Mons (after the great volcano on the planet Mars)
Omaha
Omar
Omar Khayyam
Omar Sharif
Omega
Omelet
Omen
Ometecuhtli (Aztec mythology the god of duality)
Omi
Omiros (Greek for hostage)
Omni
Omniscious
Omonoia
Onassis
Ondine
One Nut
One-eyed Jack
One-Pat
O'Mally
O'Neil
O'Roy
O-Ren Ishii (after the character in the Kill Bill movie)
O.B.
O.B. (Orange Boy
O.C. (Ordinary Cat)
O.C. (Other Cat)
O.F.C. (Our First Cat)
O.J.
O.J. Simpson
O.N.N.A.O. (Oh No, Not Another One)
O.T.M.
Oaf
Oakes
Oakichobi
Oakii
Oakley
Oakley Lucifer Fila Nike Levi Reebok
Oasis
Oatcake
Oatmeal
Oats
Obelix
Oberon
Oberon Casimir Badpaintjob
Oberon The Wonder Gut (Lord of the Faery Cats)
Oberon-Smiley
Obi
Obi Wan Kenobi
Obie (O.B.)
Obijuan
Obo
Obsidian
Obsididan
Obstinate
Ocabar
Occi
Occupant
Ocelot
Oci Osborne
Ocitar
Octavia
October
Odan
Odd
Oddball
Oddibe
Oddly McStrange
Odeipus
Odessa
Odette
Odie
Odile
Odin (Viking mythology the allmighty god)
Odo
Odyssey
Oedipus
Ofel
Ofelia
Off!
Off-License
Often
Og
Ogden
Ogies (Afrikaans for Little eyes)
Ogopogo
Oh Arrogant One
Oh Captain My Captain
Oh Oh
Oh-lee
Oi!
Oingo
Oink
Okavango
Okee
Okesha
Oki
Okie
Okinawa
Oklahoma
Okra
Oksana
Ol Yeller
Ol' Buddy
Ol' Sport
Olaf
Old D
Old Deuteronomy
Old Grandad
Old School
Old Sweetie
Old Yeller
Olde Scratch
Oleg
Oleo
Olga
Olhausen
Olia
Olimpia
Olive
Oliver
Oliver Sebastian
Oliver Stone
Oliver Twister
Olivette
Olivia
Olivia Pawdancer
Olivia The Otter Cat
Olivier Serpentine
Olja
Olla
Ollendorff
Olli
Ollie
Ollie Bollie Mc Follie
Ollie North
Ollie South
Olliecat
Oloff
Olsen.
Oly
Olympia DuKatKis
Olympician
Olympus Mons (after the great volcano on the planet Mars)
Omaha
Omar
Omar Khayyam
Omar Sharif
Omega
Omelet
Omen
Ometecuhtli (Aztec mythology the god of duality)
Omi
Omiros (Greek for hostage)
Omni
Omniscious
Omonoia
Onassis
Ondine
One Nut
One-eyed Jack
One-Pat
Oni (Japanese for 'demon')
Oni Cheeto
Onion
Onions
Only
Onnee
Onomatopoeia
Onya
Onyx
Onyx O'Kitty
Ooga-Booga
Ooh-la-la
Oona
Ooopy Poopy
Ooowwwrrraahh
Oops
Oosha
Ootzsatootsie
Oozie
Opal
Opaline
Ophelia
Opie
Opium
Oprah
Oprah Anne
Oprah Whiskers
Optimistic
Opus
Orange
Orange Blossom
Orange Boy
Orange Cat
Orange Harvey
Orange Juice
Orange Kitty
Orange Pekoe
Orange Pico
Orange Wishes
OrangEndymion
Oranges
Orangie
Orangina
Orangy
Orbit
Orca
Ord
Ordinary
Ore
Oreao
Oregano
Oreo
Oreo Bigfoot Thunderkitty
Oreo Purrowitz
Organa (named after Princess Leia Organa)
Orion
Oriondo
Orla (Irish name meaning golden princess)
Orlando
Orleans (after the city)
Orlon
Orman
Ornery
Orphan
Orphan Annie
Orphelia
Orpheus
Orpheus And Euridice
Orrin G. Cat
Orsino
Orson
Orson Winslow
Orville
Orville And Wilbur
Orvis
Osborn
Oscar
Oscar Mayer
Oscar Pisser
Osceola
Oscer
Osgood
Oshi
Osirira
Osiris
Oslo
Osman
Oso
Oswald
Otari
Othello
Other
Other Guy
Otis
Otter
Otto
Otto Octavius
Oui
Ouija
Ouisa (oh-wee-sah)
Our Gigi
Outi
Outlaw
Outrigger
Ouzo
Oven Mitt
Overboard
Overdrive
Ovid
Ow!
Owas-sa
Owen
Owl
Ox
Oxford
Oxley
Oy
Oyen
Oz
Ozma (after the character in The Wizard of Oz)
Ozone
Ozu
Ozymandius
Ozzie
Ozzy
Ozzy Pawsburn
