The wizard claiming to have flown to the moon on a Cleansweep Six is mentioned in the August or September 1995 issue of The Quibbler that Harry borrows from Luna Lovegood on the Hogwarts Express on their way back to school. According to the article, the wizard brought a bag full of moon frogs back from the moon visit to prove he had been there (OP10).
Vivid imagination, tending towards fantasy and self-delusion?
Lexicon list of Broom Manufacturers
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Harry Potter Fandom: Will Wizard ever Journey into Space?
SciFi Stack Exchange: Has the Magical Community breached the Final Frontier? (AKA Wizards in Space?)
Tags: brooms / broomsticks fantasies fantasy flying imaginary journey moon