Can anybody be put at running back?

Question

my friend is a idiot. And he said this.is it true

Answer 1

I believe the answer is yes as long as that player checks in with the refs and announces he is an eligible receiver.  

Back in 1985, the Chicago Bears would often send 320 lb. DT William "Refrigerator" Perry in at running back on short yardage situations.

Answer 2

I agree with your friend. Small runningbacks are excellent, they're elusive and generally faster. Reggie bush is like 5'7