"Couldn’t find The Great Mouse Detective but I found THIS"
IMDB description: A teenage girl living in the ruins of the Romanovs' palace finds herself running from the secret police with her four magic instruments, who are all she has left of her family, whom she can't remember. In a baggage car on a freight train, the young girl Anastasia finds the former general of the Tzar's army Vladimir Ichonovitch stowing away in a suitcase. Ichonovitch assumes from the beginning that Anastasia is out to prove that she's the heir to the Romanov throne and that she wants the fortune. Anastasia, of course, knows nothing of this but gets sucked into the con with Ichonovitch, who teaches her family history and dresses her up.
Fungus the bogeyman was first published in 1977. Created by Raymond Briggs.