Tongue twisters, or trava-línguas in Portuguese, are a fun way to improve your pronunciation and fluency in Brazilian Portuguese. Here are some popular tongue twisters in Brazilian Portuguese:

1. O rato roeu a roupa do rei de Roma. (Translation: The rat gnawed on the king of Rome's clothes.)

2. A vaca malhada foi molhada por outra vaca molhada e malhada. (Translation: The spotted cow was wet by another wet and spotted cow.)

3. Três pratos de trigo para três tigres tristes. (Translation: Three plates of wheat for three sad tigers.)

4. Pedro tem o peito preto, o peito de Pedro é preto. (Translation: Pedro has a black chest, Pedro's chest is black.)

5. O peito do pé de Pedro é preto, quem disser que o peito do pé de Pedro não é preto, tem o peito do pé mais preto que o peito do pé de Pedro. (Translation: The instep of Pedro's foot is black, anyone who says the instep of Pedro's foot is not black, has an instep that is blacker than Pedro's instep.)

6. Toda a gente tem gente que gosta, mas eu gosto de gente que gosta de mim. (Translation: Everyone has people they like, but I like people who like me.)

7. Sabendo o que sei e sabendo o que sabes e o que não sabes e o que não sabemos, ambos saberemos se somos sábios, sabidos ou simplesmente saberemos se somos sabedores. (Translation: Knowing what I know and knowing what you know and what we don't know and what we don't know, we will both know if we are wise, knowledgeable or simply knowers.)

These tongue twisters can be challenging, but with practice, they can help improve your Portuguese pronunciation and fluency.