There are several secret units that don't, at the moment of this writing, have a code to access them during games. Despite this, they can still be accessed in the editor through a simple process. First, place a unit on the map, then select the "Replace Unit" command under "Objects." In the drop down menu, select Fluffy, Flying Purple Tapir, Learicorn, George Crushington, Lazerbear, or Monster Truck A and then click replace unit.