The original "Red" boasted a phenomenal cast -- Bruce Willis, John Malkovich, Mary-Louise Parker, Helen Mirren, Brian Cox and Morgan Freeman, among other great actors. But in "Red 2," even Willis and Mirren were dumbfounded by the performance that new recruit Anthony Hopkins gives while playing a nutso bomb inventor in the film.

"At a certain point, Helen and I stopped doing our off-camera work, and we were just in awe of what Tony was doing," Willis told MTV News. "[He] referenced like three or four imaginary characters that were in the room, and I went, 'Is that in the script?' And then we just went, 'Oh, that's fantastic!' "

"Red 2" picks up where the last film left off, as Willis and his fellow "Retired, Extremely Dangerous" operatives attempt to fade back into suburban anonymity. But when Malkovich's character uncovers information that Interpol is hunting them down, he, Willis and Parker set out on the lam for a reunion with their former teammates as they try to uncover the reason why they're being pursued, while also saving London from being blown to bits.

Hopkins, who plays the creator of the explosive device that threatens London, explained that he worked with director Dean Parisot to give the character some extra little idiosyncrasies to make him especially unhinged. "I was given carte blanche to invent stuff by the director," he revealed. "It was designed with the writing on the wall, and I said, 'Can I be playing opera?' He said, 'yeah,' and there were some books.

"I just sort of reinvented the script for myself, and hoped that it would not get in anyone's way," he explained. "And Bruce and Helen were so welcoming and enthusiastic about it, I was very relieved. Very happy."

"Red 2" opens in theaters nationwide July 19.