While Leonard Nimoy's presence makes sense, a cameo from another TOS star would have been more difficult to explain. While speaking at Supernova Pop Culture Expo in 2008 (as reported by TrekMovie ...

The movie honored the classic series by casting Leonard Nimoy as Spock, linking the old and new timelines. Yet another principal star from Star Trek: The Original Series (TOS), Nichelle Nichols ...

From the first moment that William Shatner and Leonard Nimoy were filmed together on the original Star Trek, there was an instant spark and rapport between their characters of Captain James T.