Moviemaker Robert Rodriguez kept his Spy Kids 4 cast members guessing about why they were smelling so much in the film - because he wasn't ready to tell them the film sequel would be released with Aromascope.
The director told stars like Antonio Banderas and Jessica Alba of the 4D development just before he announced the news to the media last week.
Throughout the film, his stars were asked to pretend they could smell things - pleasant and unpleasant - and now moviegoers will be able to sniff along thanks to a swipe card they'll be given when they head into cinemas upon the film's release in August.
Rodriguez tells the Los Angeles Times, "They (cast) were wondering why I kept having them smell things in their scenes. I called some of them last week to tell them for the first time and they were like, 'Oh, so that's why you kept having us do that.'"
The filmmaker admits not all the scents will be pleasant: "It's a mix. There's a kid who pulls a lot of pranks, so there are a lot of smells associated with him. Some are food items, so sweet smells. Some are surprising smells."
Watch "Robert Rodriguez, Danny Trejo, Joel McHale and Jeremy Piven at"Spy Kids 4D"Premiere"