Well, if you are talking about the Sinnoh Pokedex, it is KRICKETOT. KRICKETOT's area is unknown, but you should just search the lower level areas. It is possible to catch one, because I caught a DRIFLOON at the Valley Windworks, and in the Pokedex, the area was labeled "unknown". However, if you were talking about the National Pokedex, I cannot help you. Sorry.
Kricketot
Speak to Dawn's/Lucas' little sister, she will tell you about 15 different rare pokemon.
It is in the wild in Wayward Cave B1F with a 15% encounter rate.
you have to get there by going to Celestic town and then find Mt. Coronet. when u see this give me your pal pad number by 15:45 .
If you mean buneary on diamond and pearl, I have 15 of them. buneary is a Pokemon only on Pokemon diamond and pearl
You can't find a Glameow in Pokémon Diamond. You'll have to trade it from Pokémon Pearl, where it can be found at Route 218 and Route 222, with respectively a Rarity of 15% and 20%.
You have to use the Poketransfer on route 15 from previous games (Diamond, Pearl, Platinum, Heartgold or soulsilver).
lvl 15
lv.15
Skull fossils. If you want proof, I honestly think that I have 15 cranidos on diamond.
you need to evolve a burmy which you can catch in a honey tree 15 hours after you slather honey on it (it will only be a burmy sometimes)
Starly evolves into Staravia at Level 15.