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.
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.
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 like "Wolf-Wolf"? English translations of the story have him calling himself "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. 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.
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.