A sockpuppet is a term to refer to users who have made another account to cause problems on wikis. Maybe because this user avoids a block, harass users, post vandalism or create drama on a wiki. Multiple accounts are allowed on Wikia, but they don't have to be used for the reasons listed above. However some wikis have in their policies multiple accounts are not allowed on their wiki.
If Wikia staff finds out you're abusing multiple accounts they may block you.