Okay i implemented this into my own server when i had one i think it would be a great idea.... Again this is not an event its an idea to consider.
Okay you make 4 NPCs put them all in differcent maps the one starting NPC is in twin city when a player starts the event every 15 mins it gives players who want to play an egg they have to take that egg to another npc to see if that npc wants it and so on and so forth but they have to figure out the order in whitch the NPCs want the eggs and then end NPC of course would be the Twin City NPC to give them there award but the first one to that NPC with the correct egg will get the award!
I used eggs you can use any items you want!