The mule was first introduced to residents when 1.2 was announced to the public via a newsletter which claimed residents who had lifetime accounts would recieve "40 acres and a mule". The 40 acres were recieved in the form of 4096 square meters of possible land for them to buy without any extra charge to their accounts (other than the L$ it would take to buy said land), but the mule was not delivered.
To this day, residents have yet to receive any mule in any shape or form. However, they did recieve a pony (due to the great demand given on Resident Vote in the form of Pony Linden located in Morris.
Many residents still wait in great anticipation for their promised mule to arrive. Will Linden Lab ever deliver on this promise or will it remain another myth like Havok 2, Echo Omega, and the Brent Linden cloning factory? Only time will tell!