Karl Urban nicked Bruce Willis with the cup he throws at him in their fistfight scene because he threw it faster then Willis expected. You can see the slight look of surprise on Willis's face in the scene.
John Malkovich read the first 40 pages of the script and liked it. But he asked his agent why he was up for the role of Frank. He said Malkovich had been reading the wrong lines. He was up for Marvin's role instead.
In Bulgaria the film is distributed under the title BSP (Besni Strashni Pensii - which means Furious Frightful Pensioners). But BSP is also a mock title referring to the abbreviation of the Bulgarian Socialist Party (BSP). Its political color is red and its voters are mainly elder and retired people - just like the REDs.
The purse Victoria uses as a weapon was Helen Mirren's own purse. It was given to her as a gift from Giorgio Armani. Since it went so well with the dress she was wearing, and the purse was part of the script, she asked if she could use it. The producers said yes.
Both Bruce Willis and Julian McMahon have been engaged to model/actress Brooke Burns. McMahon and Burns were later married from 1999-2001, while Willis and Burns were engaged for part of 2003-2004 but were never married.
Morgan Freeman's faux-African dictator character is driven in a Mercedes 600 Pullman limousine, a favorite of world leaders including many developing-world/Communist-regime dictators such as Nicolae Ceausescu, Josip Broz-Tito, Fidel Castro, Pol Pot, Enver Hoxha, Leonid Brezhnev, Kim Il-Sung, Jong-il Kim, Idi Amin, and Ferdinand Marcos.
In 'The Bourne Supremacy (2004)', Karl Urban plays a Russian and Brian Cox plays an American. In Red, this is reversed, with Cox playing a Russian and Urban playing an American. However, neither of these two actors hail from either of these countries, as Cox hails from Great Britain, while Urban hails from New Zealand.
When entering Frank's weapon container, Marvin picks up a submachine gun and comments that it's a "Swedish K". The weapon is a Kpist m/45, used by the Swedish military up until 2007. It was also made under license by Smith & Wesson with the designation "mod. 76". It was used by US Special Forces due to its durability under harsh conditions and it's therefore not unlikely that Marvin has used it as a service weapon.
The first feature theatrical film based on a DC comics property not made by Warner Bros.. (Batman: The Movie (1966) (from Fox) was a spin-off from a TV series, and Superman (1948) (from Columbia) was a serial.)