Make sure you do not have any conflicting scripts and the input of the pokemon is correct, it does not account for misspelled names, and it SOMETIMES is case sensitive. Instead of !pokedex Pikachu try !pokedex pikachu
I thought I fexed the case sensitivity problem, I will look at it again.
I also just noticed that you tried both variations already. I just tried it and its working on my end.
[05:57] <~T0x|cAv3ng3r> !pokedex Pikachu
[05:57] <&d3t0x_b0t> [PokeDex 1.0]--[ Searching for PIKACHU in National PokeDex... ]
[05:57] <&d3t0x_b0t> [PokeDex 1.0]--[ PIKACHU No. 025 ]--[National]
[05:57] <&d3t0x_b0t> [Type: Electric][Gender Ratio: 50% male/50% female]
[05:57] <&d3t0x_b0t> [HP: 35][ATK: 55][DEF: 30]
[05:58] <&d3t0x_b0t> [SPD: 90][SP.ATK: 50][SP.DEF: 40]
[05:58] <&d3t0x_b0t> [Height: 0.41m][Weight: 13.2 lbs (6.0 kg)]
[05:58] <&d3t0x_b0t> [Description: When several of these POKéMON gather, their electricity could build and cause lightning storms.]
[05:58] <&d3t0x_b0t> [More Info: http://pokemondb.net/pokedex/pikachu ]