Expression: Figure-toi

Meaning: guess what, get this, can you imagine, if you can believe it, believe it or not

Literal translation: to imagine

Notes: Se figurer means "to imagine, picture." The meaning of the French expression figure-toi isn't all that different so it's technically not an idiomatic expression, but it is extremely common and useful.

Figure-toi or figurez-vous is used as a sort of filler to expression surprise or mild disbelief:

   Il l'a perdu, figure-toi.
   He lost it, imagine that/if you can believe that. / Get this, he lost it.

   Figurez-vous qu'on ne peut pas y aller ensemble.
   Believe it or not, we can't go together.