"I loved him like a brother. We will all miss his humor, his talent and his capacity to love," William Shatner, who co-starred on "Star Trek" as Captain Kirk, said in a statement.
"Today, the world lost a great man, and I lost a great friend. We return you now to the stars, Leonard. You taught us to 'Live Long and Prosper,' and you indeed did, friend. I shall miss you in so many, many ways," "Star Trek" fellow cast member George Takei, who played Hikaru Sulu, wrote on Facebook.