Land of Black Gold
In "Land of Black Gold", the detectives mistakenly swallow some mysterious pills used to adulterate fuel, that causes them to sprout immensely long beards and hair that change colour constantly and grow at a break-neck pace. The condition wears off by the end of this adventure, but it relapses in "Explorers on the Moon", causing problems when Captain Haddock must continuously cut their hair, repeatedly switching back to re-cut floor length hair (and mustaches and beards) which all grow back in seconds. Frustrated at this, the captain exclaims "After all this, when they ask me what did I do on the spaceship, I'll reply 'Me, you say? I was the barber!'"