Insanity Mountain is a location on Object Madness, located in Insanity Island. In Worthless Change, the challenge was to have a team get all of it's members to the summit (and bring Penny and Nickel up the mountain to be recovered), in which Team A won the challenge.
It is a green mountain with a rocky outcrop fused into it. According to the new intro, there is water behind the mountain.
According to episode one's description, Insanity Mountain is the tallest mountain on Insanity Island.