Realizing that using a real, living lion was not possible, and since filming with wildlife is prohibited in the Amsterdam city area, the crew contacted Dutch animation director Erik De Boer, whose company was responsible for the computer-generated tiger in Life of Pi (2012). However, De Boer calculated that one scene alone with a fully computer-generated lion would cost about a million Euros (one-third of the entire budget). The crew then turned to a Dutch special effects company, who built a very detailed, manually operated animatronic lion for the close-up scenes. A computer-generated lion was used for a few scenes that showed the creature in full.
A clear Wilhelm Scream can be heard at about 1h30m when an exploding grenade blows away a member of the police unit while hunting down the lion.
It is stated at one point that the police had to help two elderly people who got stuck in an elevator. This is most likely a reference to The Lift (1983), one of Dick Maas' early movies.
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