First let me apologize for the lack of detail on this, but I was probably around 6 years old when I saw this movie. All I can remember is that the movie started out with a little boy around 6 or 7 years of age playing in his room, and there being a fire truck outside. I seem to recall the boy being transported into another world and meeting weird humonoid creatures (I think they were all short). The movie was live-action and could have been made anytime between 1980 and 1998.
I think of Time Bandits when reading your description. Only thing is that the fire truck is at the end of the movie and the boy is a little older.