If you're looking for anime similar to Shizumu, The Imaginary Girl, you might like these titles.
A new 20th century museum has opened in Khazu City! Looking like a striking replication of the 1970 World Expo, the museum quickly wins over the hearts and minds of the adult population. It becomes clear to Shin-chan that the designers of the museum have ulterior motives as all the adults flock to the museum and lose their memories, returning to the comfort and nostalgia of the 20th century. It’s up to Shin-chan and his friends to unravel this heinous plot and return their parents to the 21st century before the whole world follows them into the past!
Shin-chan and his friends discover an abandoned movie theater where some sort of western film is being displayed to an empty room. Shinnosuke's friends mysteriously disappear thus making the Nohara family start searching for them at the location they were last seen. While looking for the other kids, the Noharas inexplicably find themselves taken into the movie being exhibited.