In the arctic...

Mulder has rescued a naked Scully from her pod and put his own jacket and trousers (notice how they are a perfect fit on the 6ft Mulder as well as the 5ft next-to-nothing Scully, especially when they are lying on the ice after the space ship has gone!) on her and they are escaping the space craft.

Crawling through the ice tunnel Scully very clearly has bare feet.

However, when Scully comes round after the space ship has flown overhead to hug Mulder and now she has big thick really obvious grey socks. A parting gift from the aliens perhaps?

I know running on ice would be very cold, but they should have noticed especially as you see her feet in the tunnel and after falling down so clearly.