Mount Mushmore is a stage in C2: Judgement Clay. The stage belongs to no one in particular, but is given to a random character that you have fought already before fighting your characters boss. The clock in this arena is a banana, just like Bungle Jungle.
This stage is obviously a parody of Mount Rushmore, but upon further analysis, the four characters can be identified. It has Blue Suede Goo, Helga, Taffy, and Bonker; the characters that were not in this sequel (save for Ickybod Clay). It also appears to be nighttime; not exactly the place for looking at the stars, considering the eerie statues block most of the sky. The ground is also very mushy, like its name.