Le Passe-Muraille
While wandering around Montmartre, you might be lucky enough to bump into this great statue/sculpture, Le Passe-Muraille (the Passer-Through-Walls). Le Passe-Muraille is the title of a story by Marcel Aymé about a man named Dutilleul who discovers that he can (you guessed it) walk through walls. The statue is situated in a place named after Marcel Aymé in beautiful Montmartre.
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You can see how his lower hand is shiny from all of the tourists taking pictures pretending to pull le passe-muraille out of the wall. The statue is a bit larger than life and somewhat high up on that wall, so you really can't reach the hand that you'd actually want to pull on to help the poor guy.
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Ha, no way I'm translating all of that! Basically, Dutilleul was a lowly civil servant from Montmartre who discovers this amazing ability, and he first uses it at work to drive a middle-management-type guy crazy because he had constantly humiliated him. Dutilleul then moves on to burglaries, leaving notes signed, "Garou-Garou" — a funny name that really doesn't translate well; "Garou" is part of the French word for werewolf, so "Garou-Garou" is sort of, but not really, like "Wolf-Wolf"? English translations of the story have him calling himself either "Wolfy," or "The Lone Wolf"; much better. Anyway, he somehow gets himself caught and thrown in La Santé prison, where he soon has the audacity to escape to have lunch in a café and then send word to the prison warden asking him to come and settle the bill, haha. All right, enough translating. The story involves a love interest, of course, and lots of sneaking though walls to avoid her oblivious husband. At the end of the story Dutilleul gets himself (!spoiler warning!) permanently stuck in a wall. Hence the cool statue. The end.
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Getting there
Place Marcel Aymé is located just off of Rue Norvins, in the 18th arrondissement; here's a map pinpointing the location. There's no Métro station that's really close by, but this whole section of Montmartre is absolutely perfect for a long, winding afternoon stroll, and it's definitely worth making a note of Rue Norvins/Place Marcel Aymé on your map and working in a visit to poor old Dutilleul while you're in the neighborhood.
If you're in the area, you're just half a block or so from Le Moulin de la Galette, which is a restaurant in an old windmill! I've never dined there myself so I don't have an article about it, but I've always wanted to check it out. At the very least you should stop by and take a look at the windmill. You can find it at the same map link above.
Enjoy!