David McCallum, star of NCIS and The Man From U.N.C.L.E., has died at the age of 90. His death has prompted an outpouring of grief from fans and co-stars, with actors Wilmer Valderrama and Michael Weatherly paying tribute on social media. Valderrama praised McCallum's professionalism in an Instagram post, while Weatherly shared a video on Twitter and called McCallum a "funny fantastic authentic man." Emily Wickersham, who worked with McCallum on NCIS, also paid her respects on Instagram, calling him a "true legend."