Co-Optimus writes: "If you start up a co-op lobby, but have one or two empty spots, the unmanned characters will encourage you (in fairly irritating insults) to switch up and use them, while not actually walking around the map to attack enemies. You can change characters whenever you please, handy for unleashing these special attacks on your foes. Even the characters not being actively used will build up their special meter by automatically throwing snowballs, if you place them in a strategically sound place on the map (think of them as snarky turrets). You'll also want to keep in mind, each character has a slightly different movement speed. As an example, Hyperactive Tweak is faster than fatty Cartman, which changes how fast you collect coins, run to a position to set up more turrets, or how often you accidentally overstep and run straight into a line of enemies."