Formal:
* De grandes oreilles: This is the most literal and formal translation.
* Des oreilles larges: This translates to "wide ears" and is a more nuanced way of saying "big ears."
Informal:
* Des oreilles de lapin: This translates to "rabbit ears" and is a playful and informal way of saying "big ears."
* Des oreilles d'âne: This translates to "donkey ears" and is a more sarcastic and sometimes offensive way of saying "big ears."
The best translation will depend on the context of your conversation and the relationship you have with the person you are speaking to.