Like a more neutral style of Spanish? Well, this chunk is gonna be right up your street! You see, ¿en serio? is essentially a more neutral alternative to ¿a poco? and ¿neta?. But, worry not, it still sounds very Mexican (though, it IS used in other Spanish-speaking countries too!). It just means: 👉 Really? / Are you serious? / Seriously? 🚀 Just like its more colloquial cousins, ¿en serio? can be used as a sentence starter too: ¿En serio vas a ir a la fiesta?
Are you really going to the party? ¿A poco vas a ir a la fiesta?
Are you really going to the party? ¿Neta vas a ir a la fiesta?
Are you really going to the party? 📌 And you might also hear it with an es tacked on at the beginning! This often adds emphasis, so only use it when you're really struggling to believe what you've just heard: ¿Es en serio? Pensé que estabas bromeando.
Are you serious? I thought you were joking.