A tongue twister is a sentence that is difficult to pronounce. Usually, tongue twisters are used as games, especially to entertain children with little more than words. We have all tried to say, as quickly as possible, tongue twisters like ‘Setze jutges d’un jutjat mengen fetge d’un penjat, si el penjat fos despenjat es menjaria els setze fetges dels setze jutges del jutjat’ (Sixteen judges of a court eat the liver of a hanged man, if the hanged man were unhanged he would eat the sixteen livers of the sixteen judges of the court), and ‘Un plat pla blanc ple de pebre negre està’ (A flat white plate full of black pepper is). If we look at the characteristics of these sentences, we will find a shared element: the repetition of a sound. The repetition of a sound is a stylistic device that we call alliteration and which also occurs in poetry, as in that verse by Josep Maria de Sagarra, “Vinyes verdes vora el mar” (Green vineyards by the sea). But unlike alliteration, a tongue twister consists of the repetition, usually at high speed, of alternating sound sequences. With this system, the difficulty arises when a different but similar sound appears. If we think about ‘Un plat pla blanc ple de pebre negre està’, the mistake we usually fall into is reaching ‘pebre negre’ and pronouncing ‘peble negle’ or, if we want to prevent it, pronouncing ‘pre’ and not ‘ple’. In these cases, the ‘l’ and the ‘r’ are consonants that are pronounced by placing the tongue at the same point in the mouth, before the upper teeth. In a tongue twister like ‘De genollons collia codonys, de genollons codonys collia’ (Kneeling he picked quinces, kneeling he picked quinces) the change in the order of the word ‘codonys’ and the similarity of the first syllable with the word ‘collia’ can cause us to say “de genollons codonys codia’” or, due to the similarity of the last syllable of ‘genollons’ and ‘codonys’, to say “de genollons collons collia”. The second one will surely be the one that will make the person who challenged us to pronounce the tongue twister laugh.