Urf the Manatee Warwick is reference to the April Fool's day hero Urf. At the end of April Fool's Day 2010 it was known that Warwick had killed and flayed Urf.
The skin itself cost 5000 and was reduced by 99% for most of the available time to 50 , until it shifted to 500 . On the last weekend, it cost the actual price before turning unique. Riot Games donated the money to a foundation protecting hunted manatees.
On the Harrowing version of Summoner's Rift, if Urf's ghost is approached by Warwick wearing the Urf skin, Urf would throw his spatula at Warwick and shake his head.
in the Urf the Manatee Warwick skin a sand sculpture of a turret can be seen
Firefang Warwick is a possible reference to the mythical creature Ifrit, which is said to be a fire demon that takes the shape of a giant wolf-like creature.
Hyena Warwick has a special running animation and a diffrent laugh.
In the Taiwanese client, Hyena Warwick skin is labelled "Lv11", referencing the bounty quest target "Hogger" from World of Warcraft, the very first elite mob that most alliance players would come across and have trouble with.
Grey Warwick can only be obtained after getting 50 referrals.