Fungus the Bogeyman (2004)

BBC adaptation of Raymond Briggs' children's book. Fungus (voice of Mak Wilson)'s job is to venture above Bogeydom and scare dry-cleaners (a Bogey's name for humans). But on one trip disaster strikes and a dry-cleaner discovers their existence in Bogeydom. The dry-cleaner, Jessica (Clare Thomas), strikes up a friendship with Fungus' children and escapes back home to tell her father George (Martin Clunes) all about it. George then decides to stake-out the entrance to Bogeydom, in order to catch a real-life Bogeyman.

Unfortunately the movie Fungus the Bogeyman is not yet available on HBO Max.