From Bulbapedia, the community-driven Pokémon encyclopedia.
A WikiFairy is someone who makes large edits such as creating pages and repairing outdated ones to greatly improve the wiki.
WikiFairys are usually good at making new pages and revamping derilect ones. WikiFairys love to work in the open (making large edits) in defined parts of Bulbapedia. Look at the recent changes and you may even spot one, any edits with changes in bold usually indicate a WikiFairy.
The usertag for this is
It looks like this:
|| This user is a WikiFairy.