Learn Spanish (Spain): Nos quedamos mudos y muy sorprendidos anoche. - We were left speechless and very surprised last night.

The reflexive verb quedarse followed by an adjective is used to express a change of state or a reaction to a specific event. While estuvimos sorprendidos just means "we were surprised" (a state), nos quedamos sorprendidos emphasizes the change into that state, meaning "we were left surprised" or "we became surprised" due to whatever happened.

How do we know nos quedamos is in the past tense here? It looks like the present tense.

You are completely right! For regular -ar verbs like quedar, the first-person plural (nosotros) form is exactly the same in both the present tense and the preterite (simple past) tense. We know it is past tense here purely because of the context clue anoche (last night).

Why are both mudos and sorprendidos plural?

When using quedarse to talk about a change of state, the words that follow act as adjectives describing the subject. Since the subject here is nosotros (we), both adjectives must end in -s to agree with it. If a single woman were saying this about herself, it would be Me quedé muda y muy sorprendida.

Does mudos literally mean "mute" or just "speechless"?