Factual error: In one scene, Vada is showing off her mood ring. The movie is set in 1972 and mood rings were not created until 1975.
Factual error: The pirate ship ride was not invented until 1981; however, it appears at the carnival that is supposedly taking place in 1972.
Chosen answer: Most likely because there was no reason for a scene of them together to tell the story. It is assumed that because Thomas and Vada are friends, that Harry has interacted with Thomas many times before. There could have been scenes filmed with the two actors together that was later cut from the final film. This often happens to quicken the film's pace, shorten the running time, etc.
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