And now, here is a complete list of all my Pokemon's nicknames from Emerald and Diamond! With explanations for some!
(Pokemon with red species names are female; blue ones are male; green ones are genderless.)
Note: You can find a lot of the following especially:
-Harry Potter characters (their nicknames have an asterisk next to them, in case you're confused)
-People's names which sound like a characteristic of the Pokemon (their explanations have asterisks at the end)
-Pokemon trainers (I think you'll be able to identify these, as each is named after someone who has that Pokemon)
Note: My Pokemon who have lousy in-game-trade names or are unnamed as a result of trades/events are not included. That would be an Alakazam (Kazza), Chatot (Charap), Darkrai, Deoxys, Manaphy, Snorlax, Infernape, Empoleon, Bastiodon, and Purugly.
Raichu: Raiha
Raichu: Lt. Surge
Clefable: Cupid
Ninetales: Naruto
Jigglypuff: Purin (Jigglypuff's Japanese name)
Vileplume: Fleur (French for flower)
Golduck: Ruby (because of the gem on her forehead)
Alakazam: Hermione*
Tentacruel: Ursula (The sea witch in Little Mermaid)
Tentacruel: Neptune
Rapidash: Cinderella (emphasis on the "cinder"*)
Magneton: Gamma (One of the Magnet Warriors in Yu-Gi-Oh)
Gengar: Seirei (Japanese for spirit)
Electrode: Pokeball (I often LOL when this Pokemon comes out in battle--"Go Pokeball!")
Seadra: Misty
Seaking: Elan
Starmie: Hoshi (Japanese for star)
Mr. Mime: Marceau (named after Marcel Marceau, a famous mime)
Gyarados: Serpentina
Noctowl: Frau Nacht (in German, it means something like "Ms. Night")
Crobat: Lilith
Xatu: Clair (As in short for clairvoyance, not the gym leader.)
Bellossom: Benito
Azumarill: Bunny
Azumarill: Bob (because his tail bobs up and down on the water*)
Quagsire: Marsha (Quagsire lives in a marsh*)
Wobbuffet: Retalia
Girafarig: Giuffrida (Sounds like giraffe*)
Girafarig: Primrose
Steelix: Platinum
Heracross: Tsunoko (making a Japanese girl's name out of the word "tsuno"--horn)
Heracross: Prongs* (Although technically, the name makes more literal sense--horn = prong?)
Sneasel: Fred* (Yes, I also have one named George!)
Corsola: Kaminda (In a language I sort of created, it means "pink")
Octillery: Octavian (I know it's ridiculous for an octopus to rule Rome, but at least the "Oct" makes sense!*)
Mantine: Katie (Sort of looks like "kite"*)
Skarmory: Knightwing
Donphan: Fanta (Not to be confused with the soda. Ellie is too cliche anyway.)
Blissey: Florentine (Also an egg dish)
Blaziken: Doodle (Short for ****-a-doodle-doo)
Mightyena: Artemis
Linoone: Hufflepuff*
Beautifly: May
Beautifly: Shumi (Anagram of "mushi", Japanese for bug)
Dustox: Doxy* (It's more of a creature than a character per se, but...)
Dustox: Pesto (Because a moth is a pest! Oh! Sauce? 0_e)
Lombre: Lolita (Spanish name that looks like "Lotad"*)
Nuzleaf: Pinocchio
Swellow: Robin (Seems to resemble a robin, doesn't she...?*)
Pelipper: Phyllis (A pelican from Animal Crossing)
Gardevoir: Sigmund (As in Freud, but the last name sounds too weird to put in a nickname)
Masquerain: Drew
Breloom: Portabella (because Portobello sounds too masculine)
Ninjask: Arya (the elf from Eragon--don't ask why I named a Ninjask after an elf...)
Shedinja: Fiari (In a language I sort of created, it means "ephemeral" or "not quite there")
Exploud: Muffliato* (actually a spell that prevents you from hearing something)
Hariyama: Luchadora (Spanish for wrestler)
Delcatty: Tom-Tom
Sableye: Gollum (shiny-object-lover from Lord of the Rings)
Lairon: Haganiwa (from the Japanese "hagani"--steel and "iwa"--rock)
Medicham: Satori (a sudden spiritual awakening or vision)
Medicham: Mahatma
Manectric: Leona (Spanish for lion, which Manectric seems to resemble)
Plusle: Rachel (named after my stepniece, who is a cheerleader)
Minun: Cheerum
Volbeat: Hikaru (similar to hikari, which means "light"*)
Illumise: Starlet
Roselia: Rosemary (I know that's a spice, not a flower, but girls are made of spice... right?)
Sharpedo: Amazon (Leftover from when she was a Carvanha, obviously)
Wailmer: Moby Dick
Camerupt: Magmus (Just sounded more, erm, sophisticated... than "Magma")
Torkoal: Pele (Hawaiian volcano goddess)
Grumpig: Miss Piggy
Spinda: Confundus* (Another spell, which causes confusion)
Vibrava: Sylph (Flying mythological creature)
Cacturne: Harley
Altaria: Cumulus (type of cloud)
Seviper: Nagini*
Lunatone: Yue (Chinese for moon... I think)
Solrock: Domingo (Spanish for Sunday)
Barboach: Feely
Whiscash: Quaker (Not to be confused with the religion or the oats!)
Crawdaunt: Langosta (Spanish for lobster)
Claydol: Clayton
Anorith: Sebastian (The lobster or whatever from Little Mermaid)
Milotic: Venus (Also makes sense because of the famous statue Venus de Milo...tic)
Castform: Weatherman
Kecleon: Nymphadora*
Banette: Severus*
Dusclops: Samara (the girl from The Ring)
Tropius: Fern
Chimecho: Tinkerbell
Chimecho: Belle
Absol: Sirius* (It can also be noted that the Egyptians used to see the star Sirius as a warning that the Nile will flood)
Glalie: Yukiko (in Japanese it literally means "snow child"*)
Sealeo: Saki (a famous sea lion who appeared on television)
Luvdisc: Roxie (because of a character in the musical "Chicago" named Roxie Hart)
Torterra: Pangaia (A dub name I came up with for this Pokemon, from the continent of Pangaea and the goddess Gaia)
Staraptor: Silverling (A dub name I came up with for Staravia, short for "silver starling")
Bibarel: Beatrice (sounds similar to beaver)
Kricketune: Katydid
Luxray: Godric*
Roserade: William (because his nature says "strong willed"*)
Rampardos: Yoshi
Wormadam-Grass: Mistletoe (Burmy's appearance reminded me of mistletoe)
Wormadam-Ground: Cleopatra
Wormadam-Steel: Jasmine (Jasmine doesn't have a Wormadam, but she likes Steel Pokemon nevertheless...)
Mothim: Thatcher (Has nothing to do with Margaret Thatcher. The name just sounds cool, and includes "hatch", which is sort of what Burmy does when it evolves.)
Vespiquen: Elizabeth (Okay, but I feel justified in naming a Pokemon after an English queen for some reason.)
Pachirisu: Chip (I do have another named Dale!)
Floatzel: Ginny*
Cherrim: Shigatsu (Japanese for April, when cherry blossoms bloom)
Gastrodon: Slughorn* (Like Prongs, it makes more literal sense, as Gastrodon is a slug and appears to have horns)
Ambipom: Nimble
Drifblim: Inflotion (A dub name I came up with for this Pokemon, putting "float" inside "inflation")
Lopunny: Peter (after Peter Rabbit)
Mismagius: Maleficent
Honchkrow: Raven
Skuntank: Nox* (Yeah, I know it's a spell--one to put out light, appropriately--but it's actually short for "noxious")
Bronzong: Simuri (In a language I sort of created, it means "mirror"; I named it when it was a Bronzor)
Spiritomb: Morticia (from the Addams Family)
Garchomp: Saphira (Eragon's dragon)
Lucario: Zorro (Spanish for fox, as Lucario looks foxlike to me)
Hippowdon: Sandy
Drapion: Claudia (includes "claw"*)
Toxicroak: Bellatrix* (because Toxicroak's cry sounds like how she might laugh)
Carnivine: Maude (includes "maw"*)
Lumineon: Butterfin (a dub name I came up with for this Pokemon--"butterfly fin")
Abomasnow: Tannenbaum (German for Christmas tree, as far as I know)
Dialga: Kingmond (A dub name I came up with for this Pokemon--"king diamond")
Uxie: Zelda
Mesprit: Link
Azelf: Ganondorf
Phione: Aqua
And some nicknames of other Pokemon from my other games I like:
Empoleon: Ukio (the emperor from Samurai 7)
Wobbuffet: Jessie
Chimecho: James
Happiny: Sunny Side
Banette: Lucius*
Buizel: Ron*
Sneasel: Percy*
Uxie: Dumbledore*
Azelf: Dobby*
Purugly: Minerva*
Gible: Draco* (although technically, it makes sense because Gible is draconic)
Kadabra: Sabrina
I also have a full Unown alphabet in Diamond, and all of them are nicknamed. But their nicknames start with their letter and represent their Hidden Power type. For example, a J Unown with HP Psychic would be Jean Grey, an A Unown with HP Steel would be Aluminum, a Q Unown with HP Bug would be Queen Bee, and a n H Unown with HP Flying would be Hikou. Sometimes I can't come up with a good name and end up with something like Z-Rock. My question-mark Unown is Flying? and my exclamation Unown is Fighting!.