When Cooper examines Laura's body for the first time, he turns to a doctor and asks him to leave him and the sheriff alone with the body. The actor, mishearing the line, replies "Jim" - his name. Cooper pauses for a moment and repeats the question and the actor apologizes and leaves. According to commentary on the 2007 DVD release, this was a genuine blooper but director David Lynch liked the surreal moment and kept it in the finished product. According to the same commentary, the flickering fluorescent lights were genuinely malfunctioning but Lynch felt it helped the scene so chose not to replace the lighting.
Not long after the class scene where Donna starts to cry and James breaks his pencil when they have a premonition about Laura Palmer being dead, Principal Wolchezk makes an announcement. With the previous scene in mind, he tells about Laura Palmer as their classmate, whilst actually the announcement is meant for the whole school.
Joey Paulsen takes Donna out of the Roadhouse brawl to go meet James, driving away and being followed by Agent Cooper and Sheriff Truman. When a shot establishes the bar brawl is continuing, Joey and Donna are seen sneaking out past the bartender again.
Laura Palmer's body is found on what is supposedly a lake shore in front of the Packard home. During the filming sequence however, the tide lowers and the shore becomes more exposed - a highly unlikely occurrence on a lake. The scene was filmed at the Kiana Lodge on Agate Pass in Puget Sound and between takes, the tide went out.
The goof item below may give away important plot points.
Crew or equipment visible
At the end of the pilot, Sarah Palmer wakes up from the sofa screaming due to her vision. In the mirror above the sofa, you can see a reflection of on-set-dresser Frank Silva, who will play Bob later in the series. Silva was there to assist Grace Zabriskie with her performance by recreating the scene in her vision (UK version of pilot).