Less than a week before shooting was to begin, the people who owned the original choice of location for "Tibby's house" decided they didn't want a film crew inside their house after all. The filmmakers quickly found a new location for the living room scene and built Tibby's bedroom on a soundstage.
Director Ken Kwapis never used the traditional phrase "Action!" to begin the actors' performance on set. Instead he said, "Quiet, please, and um, uh, g'head." This method was much more relaxed and allowed the actors to begin at their own pace. However, he did get teased about it - someone even printed up bright orange T-shirts quoting him and handed them out to the crew.
During the dinner scene with America Ferrera's character and her father's new family, Bradley Whitford began doing improv and kept the entire crew laughing, making it difficult for everyone to get through the scene with a straight face.
The Pants Manifesto scene (at Gilda's) was filmed by placing the camera on a 360-degree dolly track around the girls. However it was virtually impossible for the camera to complete the circle around them without its own shadow being visible at some point in the scene (as the camera passed in front of the lights). Luckily, the visual effects people came to the rescue and "erased" the shadow from the shot.
The scene where Tibby and Bailey lie out in the park staring up at the sky full of stars and talking about life and death was shot inside on a soundstage. Parts of the movie was shot in and around Vancouver, British Columbia, Canada, and shooting on the soundstage saved the actors and crew from having to work outside in the cold Canadian night. The scene where Lena is trapped underwater was filmed in a tank on the same set.