Aliens can’t get through the Van Allen belts without frying. Neither can our astronauts. Heck…we can hardly rendezvous with the ISS. That said, there are demon spawn walking around…
There is no space agency or astrophysicist who says the Van Allen belts are like a microwave oven. They are low level radiation only, and easily traversable. An astronaut could spent as long as two weeks within them before getting sick, with only a little shielding. The idea that they will fry you instantly is just one of the false arguments made by moon landing deniers.
Have you ever worn a belt? If so, did it encapsulate your whole body?