Pokemon likes a certain pokeblock depending on their nature. it has nothing to do with what pokemon it is. Ultimately a Pikachu can like any color of blocks. For example: a Pikachu that likes to eat pink pokeblocks will also like to participate in cute contest, and etc... go to meowth's site for more info. Here is a rip from pokefor so give all credit to meowth. (view attachment. meowth's site isn't suppose to be very stable at the moment so...)
Shedinja- awesome pokemon if used correctly. it's 1 hp only but it can't be damaged from any move that isn't super effective (status effect moves excluded)
moves that kill Shedinja- fire attacks, ghost attacks, dark attacks, rock attacks, hail, sandstorm, poison/toxic status, will o wisp, curse, perish song, possibly confuse ray, flying attacks, struggle, bug attacks, spike
move that may kill Shedinja (i'm not sure about this one)- leech seed
EDIT: Right Kairi... how the heck can i forget spike... *adds to list*