In the latest segment of Le Jour où tout a basculé - J'ai piégé mon fan, Alex uses a phrase whose meaning may surprise you:
Mais bon, c'était pour la bonne cause. -Tu m'étonnes. Regarde.
But OK, it was for a good cause. -You're not kidding. Look.
Cap. 7-8, Le Jour où tout a basculé - J'ai piégé mon fan - Part 7
The literal translation of tu m'étonnes is "you surprise me," but it's often used as a set phrase meaning "you're not kidding," "no kidding," or "tell me something I don't know." Used in this way, it has the opposite meaning of its literal translation—the person is not surprised by what they just heard. Tu m'étonnes is very similar to the English expression "surprise, surprise," which is also used ironically to convey a lack of surprise.
Sans blague is another phrase meaning "no kidding" or, more literally, "no joke." This one, however, can express surprise:
Je suis né le 3 novembre. -Sans blague! Moi aussi!
I was born on November 3. -No kidding! So was I!
The verb étonner has the same root as the English verb "to stun." It means "to surprise," "astonish," or "amaze":
Sur l'eau, il vit son reflet, totalement étonné
In the water, he saw his reflection, totally surprised
Cap. 29, Contes de fées - Le vilain petit canard - Part 2
Les héritiers de Jules Verne n'ont pas fini de nous étonner.
Jules Verne's heirs have never ceased to amaze us.
Cap. 26, Le Journal - Le record du Tour de Monde!
And the English "surprise" comes directly from the French surpris(e):
Je suis un peu surpris.
I'm a little surprised.
Cap. 38, Lea & Lionel L - Le parc de Bercy - Part 1
Unsurprisingly, the verb surprendre means "to surprise":
Tu vas mener l'attaque pour les surprendre.
You're going to lead the attack to surprise them.
Cap. 28, Il était une fois - les Explorateurs - 15. Bruce et les sources du Nil - Part 2
But it can also have the related meaning "to catch," "come upon," or "discover":
Louise surprend René et Edna en pleine conversation.
Louise catches René and Edna deep in conversation.
Cap. 2, Le Jour où tout a basculé - Mes grands-parents sont infidèles - Part 8
Just as there are two words for "to surprise" (étonner and surprendre) and two words for "surprised" (étonné[e] and surpris[e]), there are two words for "surprising":
C'est pas étonnant que beaucoup de peintres soient venus s'installer ici sur Arles.
It's not surprising that many painters came to settle here in Arles.
Cap. 12, Arles - Un Petit Tour d'Arles - Part 3
C'est un endroit vraiment surprenant en plein cœur de Paris.
It's a really surprising place right in the heart of Paris.
Cap. 14, Voyage dans Paris - Les Secrets de Belleville
Can you guess what la surprise and l'étonnement mean? Surprise, surprise!