These trap doors lead to the basement of the mall, where there lurks a mutant beast, half-snake, half-man, who kills and eats the women who fall through.
One version of the rumor claimed that the snake-man was actually a mutant offspring of the Gokongwei family, and the trap doors had been installed as a way of caring for it. That's why the R of the Robinson's logo is in the shape of a snake.
Another version had it that the Robinson's Galleria fitting room mirrors were actually one-way windows, from which the snake-man could view its prey before activating the trap door. Milder variants claimed the one-way windows were merely for the lewd enjoyment of people watching from behind.
This is one of the vintage urban legends of Metro Manila, with all the classic elements of outlandish horror and even some scandal. Such strangeness was passed on for years, and is still joked about today.
Needless to say, there were never any headlines about people mysteriously disappearing from the ladies' fitting rooms in any Robinson's mall, and no one has ever seen or heard from the mutant snake-man.
As for the one-way window rumor, the best way to confirm this is with the "fingernail test" for mirrors. If, when a finger is pressed to the glass, there is some space between the finger and its reflection, it is a mirror. If the reflection touches the finger, it might be a one-way window. So far, no one has reported a one-way window in any of the fitting rooms.
I emailed Robinson's Land's PR Department for an official statement debunking the rumors of trapdoors and snake-men in their malls. It was hoped that an authoritative press release would reinforce the safety and good-standing of the mall to the public.
Here is the exact text of their email response, word for word:
"We would rather not say anything about an issue. Have a good day."
Robinson's Land Public Relations,
Make of that what you will. It is my humble opinion that Robinsons Land's PR Department needs lessons in proper etiquette, so as not to scare away customers and urban legend hunters with curt, cryptic statements like this.