Anyway, so I was looking at the breeding system in the Pokemon games (so far, may change in Gen VI) and I found a few interesting discrepancies.
If you don't do Pokemon and my two-word descriptions aren't enough to get an idea of how weird these combinations are, feel free to google names, because I'm too lazy to link all of these to images. 'K here goes.
-Cacturne (scarecrow cactus), in addition to any plant-based Pokemon you care to name that isn't really strange, can breed with: Sableye (underworld ghoul), Toxicroak (combat toad), Lucario (jackal), Volbeat (firefly), Spinda (stoned panda), Bisharp (badass chess piece), Beeheeyem (alien), Mr. Mime (harlequin), Infernape (fire-crowned monkey), Jynx (controversy), Hypno (hypnotic dream-eating pedophile tapir), Machamp (four-armed blue man-lizard), this and this
-Mareep (electrocuted sheep) can make love to just about anything with a spinal cord: Wailord (whale), Arbok and Seviper (snakes), Farfetch'd (onion duck), Psyduck (kappa platypus), Feraligatr and Krookodile (crocodiles), Charizard (everyone's favourite), Torchic (KFC), Walrein and Dewgong (seal things), Diglett (head), monkeys, lizards, rhinos, camels, dragons, tortoises, cats, mongoose, and (almost) all other vertebrate Pokemon that aren't fish, amphibians, dragons, or flying birds
-Shroomish (fungal puffball Scrooge), despite having basically no appendages, can breed with: Pikachu (yes that), Abomasnow (yeti), Torterra (world tortoise), Delcatty (cat), Tropius (banana dinosaur), Serperior (anaconda), Exeggcute (psychic eggs), Granbull (giant bulldog), Maractus and Cacturne (humanoid cacti), Glalie (terrifying ice mask), Phione (sea slug fairy), Pachirisu (squirrel), Lilligant, Roserade and Bellossom (dancing flowers)
-Glalie, the aforementioned terror mask, can breed with not only Shroomish, Pikachu, Delcatty, Granbull, Phione and Pachirisu, but also: Sudowoodo (fake tree), Bronzor (old mirror), Azumarill (water bunny), Vanniluxe (deformed ice cream), Steelix (snake made of diamonds), Garbodor (trash bag), Clefable (moon fairy), Cofagrigus (sarcophagus), Ferrothorn (spikey vine fruit), Dwebble (hermit crab), Golurk (ghost robot), Hoppip (flying pink seed adorableness), Magnezone (UFO), Porygon-Z (glitchy data), Probopass (moai), Claydol (clay eldritch abomination), and Shedinja (undead insect)
-Gastrodon (three-eyed sea slug) is just... Wut: Magcargo (lava snail), Chimecho (wind chime), Clamperl (oyster thing), Cofagrigus (sarcophagus), Octillery (octopus cannon), Castform (cloud), Reuniclus (amoeba), Corphish (crayfish), Masquerain (moth), Lotad (lily pad), Chandelure (chandelier), Rotom (electrical appliance), Politoed (rain frog), Jellicent (jellyfish), Drifblim (balloon), Empoleon (penguin), Wobbuffet (punching bag), Swanna (swan), Weezing (three-headed pollution), Eelecktross (lamprey with arms), Carracosta and Blastoise (fossil and mecha turtles respectively), Mismagius (ghost witch), Bidoof (derp), Walrein and Dewgong (sealey walrusey things), Milotic (mermaid serpent), Kabutops (fossil badass), Kingdra (seahorse dragon), Dragonite (plush dragon), Palpitoad (deformed lump), Mudkip (overused meme), Stunfisk (landmine flatfish), and this
-Ditto (purple chewing gum) can breed with all of the above and more, but it's a shapeshifter so it doesn't count.
Also, most of the above can breed with each other.