You can get this pretty much right off the bat. When you get access to your pod, instead of going up to the controller to select which planet you want to go to, open your menu thing by pressing
and select the character option. Choose Swoop and you will immediately become him without having to unlock him first.
Keep in mind this will only allow you to become him in the pod area, not in the actual adventure mode. You will still need to unlock him throughout regular gameplay.