Trivia: When Ted pulls into the rest area and the actors are not yet visible, the hitch hiker asks Ted what his car seats are made out of cause they're itchy. But if you look at the hitch hikers face as the camera pans inward toward the car, the hitch hiker's expression does not look like he just asked that question. That line was added in later because the directors thought it took too long for the car to pull in.
Trivia: Some people may have missed this reference. In the scene after Warren gets hit in the eye with the baseball, Ted shows up at Mary's house with a ball, and says "signed by Tony Conigliaro... shipped up from Boston." Conigliaro was a baseball player with the Boston Red Sox who suffered an infamous black eye after getting beaned with a pitch.