Answer:
The costume of the Cowardly Lion was made of real lion skins. It was heavy, hot, suffocating, and uncomfortable to wear. A particular problem was the heavy weight of the costume. At 50 pounds, the costume was a burden with every move and every non-move.
According to TNT the costume weighed in at a whopping 90 pounds. This answer was given in a trivia break during TNT's presentation of the Wizard of Oz.