Formal:
* São loucos: This is the most literal and formal translation. It means "they are crazy" and is appropriate in most situations.
* São insanos: This means "they are insane" and is more formal and serious than "loucos".
Informal:
* Estão doidos: This means "they are crazy" in a more informal and playful way.
* Estão malucos: Similar to "doidos", this is a casual and slightly more slangy way of saying "they are crazy".
* Estão pirados: This means "they are going crazy" or "they are nuts" and is more informal and colloquial.
* Estão loucos de pedra: This literally translates to "they are crazy as a rock" and is very informal and expressive.
Other variations:
* Estão completamente loucos: "They are completely crazy"
* Estão fora de si: "They are out of their minds"
Remember to consider the context and the audience when choosing the best translation for "are crazy".