A dark French movie about a little girl, a big guy, and a mad scientist

Question

After idly combing through this site's questions and answers, my mind is being triggered into recalling fragments of things I can't place names on. There's this French movie (dubbed in English) I saw on VHS so I believe it was mid to late 1990s, about a little girl and a big strong guy. Here's a list of things I remembered but probably not in chronological order:

• The protagonists were a dark haired little girl and a big really strong man looking for a little boy who was kidnapped by a bizarre mad scientist.
• The antagonist (the mad scientist) was experimenting on children he kidnapped and used a machine that made them turn old while it made him young ... I think.
• The setting was a dark and rundown port city and I don't even remember if there was a scene taking place during the day. So either the story took place in a span of a night or it's a place where the sun never graces its shores.
• I remembered they were being hunted down by a pair of crazy female Siamese twins. They had a organ grinder that they used to control fleas to attack the heroes.
• The big man (or was it the girl?) used a big freighter ship to run the twins down ... I think.
• They eventually ended up on an island/laboratory of the mad scientist. I think the little girl was captured and experimented on. The tables turned on the mad scientist because of the little girl's incredible will made the machine backfire on him. I think she ended up as a full grown adult and the mad scientist a mind addled idiot or vegetable.
• The actor who portrayed the big guy I think is an American actor, if I knew his name, I probably could find the movie easily ...

I hope the information is enough to go on, that's as much as I can remember after 15+ years.

Answer 1

This is La cité des enfants perdus (released as The City of Lost Children in the US) from 1995. From the Wikipedia page linked:

From an ocean rig, a demented scientist, Krank (Daniel Emilfork), kidnaps children from the nearby, unnamed port city to steal their dreams, as he is incapable of having dreams of his own. Among them is the adopted little brother, Denree (Joseph Lucien), of carnival strongman and former whaler One (Ron Perlman), who sets out to rescue him with the help of a little girl named Miette (Judith Vittet), a member of a thieves' guild composed entirely of orphaned children. They delve into the world of a bio-mechanical kidnapping cult and discover the connection between the scientist and the missing Denree.

The excerpt above covers most of the plot points you mentioned. The article continues on to mention the conjoined twins, the fleas and the organ grinder:

Conjoined twins known as the Octopus (Geneviève Brunet and Odile Mallet) control the thieves' guild, but have become distrustful of Miette; when One accidentally bursts in and shows his strength while they are planning a heist, they hire him to help the children steal a large, heavy safe. The safe is successfully stolen but then lost into the harbour when One is distracted by a sign of Denree's kidnappers; the Octopus then believes Miette has been holding out on them and has deserted to help One. They employ circus performer Marcello (Jean-Claude Dreyfus), who was their former boss and possible captor but is now apparently in their debt, to return One to them, and much to his own distaste he allows Miette to drown while rescuing One from the cult (who have captured Miette and One attempting to rescue Denree, and plan to execute them both by drowning them in the harbour) using a system of mind control involving trained fleas, a special serum, and a music box.

And the big guy is American actor, Ron Perlman.

Trailer