Board Thread:Naruto Discussions/@comment-9782468-20140811214915/@comment-24068519-20140812094150

Actionmanrandell wrote: Uchiha913 wrote: The Sharingan can't copy something like the Rasengan especially with no hand signs. He did copied it just not the Sharingan way, Minato taught it to him.

a technique doesn't require hand seals for it to be copied

Pretty sure the Sharingan only copies hand seals and body movements.