While the prospect of driving around in a car and freely switching between the foreground and background of stages sounds great on paper, the integration was lacking and these areas don't stand out nearly as much as the Jet sections. (nintendowire.com)
You could slowly chip away at his health using normal attacks, but observant players will notice the background of his stage resembles a baseball stadium. (gamesradar.com)
As mentioned before, Copper has a chance of appearing in the background of the stage Smashville, but only in the Wii U version. (nookipedia.com)