Can't help but notice...

Why does Chep know the inner cavities of the prop house better than its “owners?” This prop house is the entangled, web-like inner workings of a damaged mind. Consider that his whole life revolves around the cinema. He lives and breathes the lines of the old Hollywood stars and starlets. The prop house and all its mountainous cinematic artifacts that he scurries around in like a field mouse is a very familiar terrain for him. Even the owner and his crony pals make up this cerebral extension of the only thing Chep has ever made earthly contact with – the cinema. The Chep that is introduced to us is the Chep that has manifested to shield and protect himself, and sometimes confront hints of a reality he will never be able to confront. The Chep that we are introduced to is a true innocent. A pleasant sweet boy with amiable qualities that elicit the protective spirit in anyone who meets him.
Enter Ann, the true victim of Chep, and the only other real character that we the audience get to observe. This is the sweet girl at the ticket counter of the cinema. This is likely the only person he would likely be drawn out of his comfort zone with, as she desires to draw him out. She wants from him what, fortunately for him, no one else has ever wanted. He may even return her feelings initially. It is actually she who would likely invite herself into his humble company inside the cinema. It seems as though they have between them a brief history, a courtship. For whatever reason, during their final visit in the cinema, things go wrong and her life is terminated inside that vacant cinema where she has been employed. As his conscience resurfaces and he realizes his crime, he deeply regrets what he’s done. He may have even experienced what he felt was true love with her. He hoped he could allow himself to be drawn out by Ann. In the end he is just too fractured to step outside the only comfort zone he knows, the lives he can’t intrude upon, the lives he views on screen.
The mask that Chep wears gives him a sense of safety and protection - courage to face confrontations he’s now being cornered to fight through. The mask is of the actor Tor Johnson from the 1959 movie Plan Nine from Outer Space. Again, this would be within the era of movies that Chep resonates with.
The only true relationship that Chep has with Detective Phil is rendered through the big screen night after night. For Chep, Detective Phil is the ideal version of an approachable detective who has proverbially stepped down from the silver screen to rewrite Chep’s experience with otherwise aggressive, mocking detectives he is likely encountering. While "visiting" the prop house, ‘The Good’ Detective Phil reveals to Chep that he is enthralled with cinematic relics when he obsesses over the Purple Septor. This echoes his singular role in Chep’s life – that of a cinematic star.
While he is there, Detective Phil questions Chep about stolen items, body parts, eyeballs namely. I believe this conversation is real but the Detective Phil that Chep is encountering in the prop house is a delusional representation of a real detective he encountered in reality some time in the real past, possibly in an interrogation setting. We are viewing fragmentation, distortion, and compartmentalization of a mind that has become so good at protecting itself from the truth. His mind has assigned a stream of subconsciousness to deal with what must be regret and total rejection of a crime so heinous to Chep’s sensibilities that he has disconnected himself from his crime all together.
The re-animated, disquieting zombie like skeletal frames of beings made of bits and parts, details of cinematic breadth not over looked by an obsessive mind, speak AT him of his fears, obsessions, confusion. We know he’s gone crazy, but WE don’t know we are already in…in with him, as Jennifer Lopez was “in” in The Cell. Again, there is no “Prop House.”
The story is said to revolve around the mission of finding the strange random items that Fran requests. These items conspicuously include a prosthetic arm, a human finger, a pair of rhinoceros eyes. These items represent Ann’s remains. Fran doesn’t exist in Chep’s real life. Fran is simply one of his adored screen stars. He sees her on the big screen night after night. Chep’s fragmented delusional mind has allowed him to replace a now lifeless Ann with Fran. Although it is Fran who comes to him night after night in hopes that he can help her with her requests, Ann is the true (dead) weight leaning on his conscience. Ann and Fran’s names even end up being coincidentally similar.
It is Ann’s presence in his labored mind that is a constant reminder that will not let him rest until she is recovered and laid to rest. He must recover these miscellaneous body parts that he has removed and presumably misplaced. The process of him scurrying through the clutter of the prop house to recover these items is just a metaphor for his internal struggle to confront this desecration of Ann. He likely only deals with this confrontation during police interrogations. He wants Ann to have rest. He may at times be trying to reverse what he’s done in hopes that it’s all just a nightmare. He feels the least he can do is return her body to some form of decency for her.
The dolls in Fran’s dollhouse take on a creepy quality of post mortem bodies when the camera pans in close. They also now have rhinoceros eyes set in their heads – another macabre reminder of one of the body parts Chep has no doubt been interrogated about. Chep has the horror to view himself, his murderous self at home in his house of horrors, making love to Fran/Ann amongst this macabre setting. You start to really see Chep coming face to face with his de facto self many times. He always squirms in fear any time he is forced by his consciousness to confront his own delusional recollections of events that he has already lived.
As a final footnote, in the scene where chep speaks to Ann something extremely random takes place in the film. Chep is blindsided by a naked streaker. He’s knocked off his feet and to the ground in fact. This could have a poetic representational quality to it if you can look beyond the ridiculous randomness of it. This could represent the moment Chep lets Ann in to see his vulnerability, something he’s never done. Just as he returns the engagement of conversation with Ann he experiences an overwhelming exposure of himself in doing so. At the end of the movie, when he finally gives Ann the carousel, the streaker can be seen running behind him again. This time they never collide. Chep is beginning to adjust to the things that he has never been able to accept have taken place.