Despite popular belief, this is not a movie based on the cartoon series, it's the other way around. The movie went into development in 1985 and was released in 1986 with an intention of leading into a live action series. Instead it became a cartoon series in 1987 but did not follow the origins of the movie. Instead of Max becoming a monster, the main character became Monzi, a small cute and friendly monster from another dimension who befriends a boy named Max and his friends.
A plushie of the monster can be seen in the 1987 movie Adventures in Babysitting.
The establishing shot of the Museum that they go to in the beginning is the Lillian Massey Building in Toronto.