Tom actually showed up on set in the Captain A…

Tom actually showed up on set in the Captain America suit. Everybody said “Tom, it’s not actually going to be you though” and he said “No, no! This is my one chance to wear the Captain America suit.” – Chris Hemsworth

The fact that [Tom] had [auditioned for] Thor, that he had swung the hammer around, I thought would be great because it meant that there was a little bit of Loki that always wanted to be Thor and a little bit of Hiddleston that always wanted to be Thor as well. – Kevin Feige