Maybe he has a treadmill sideways against the refrigerator door, so when it goes forward or backwards it opens/closes the door. And each shelf in the refigerator has a tiny treadmill on it so it dumps everything onto the big treadmill when it turns on. And all of the treadmills are remote controlled.

The delivery person

But then who is putting everything on the treadmills on the other side?

he has a yellow inserter that will pick up food from the fridge and insert onto the belt