Stomples Day
This opens up on April 1st each year, lasting for the usual couple of weeks. There is a single quest for the achievement, given out by Grundle Cogwelder in the Plane of Knowledge. Grundle hangs out near the Ak’Anon stone, and gives out the quest The Origin of the Cuniculus. This may sound obscene, but it actually part of the Linnean name of the rabbit (oryctolagus cuniculus), and probably refers to the burrows they make.
You have to collect eight types of brightly coloured ground spawn eggs, from Plane of Knowledge, Qeynos Hills, West Karana and South Karana. There are a large number of spawn locations, and I have always been able to gather all I needed from Plane of Knowledge and Qeynos Hills; there may be four types only available in each zone. There are many spawn points in the Plane of Knowledge, but fewer in the others. In Qeynos Hills, around the Sayers house, at the entrance to Blackburrow, and in the undead ruins. In West Karana, look in the guard towers and in and around the barbarian fishing village.
The reward is Madness of Stomples, a clicky that generates rabbits, and sometimes a self-illusion of a rabbit. Enchanters can hand this in to get a rabbit illusion spell!