In fact, the game TELLS you "This disc can only be used in Toybox mode".... Repeatedly. To the point that it's annoying. (even in the toybox hub.. so it's really not all that clear). What I don't get.. I can't use a Y-Wing in Toybox Hub but in my farm it's completely acceptable.
Yeah I tried using Grievous's Wheel Bike and it would spawn. So maybe certain things only work certain places, even in Toybox.