They were just shitfaced. (Speaking in tongues follow-up)

When they heard this sound, a crowd came together in bewilderment, because each one heard their own language being spoken. Acts 2:6 We hear them declaring the wonders of God in our own tongues!" Amazed and perplexed, they asked one another, "What does this mean?" Acts 2: 11-12 Some, however, made fun of them and said, "They have had too much wine." Acts 2:13 Then Peter stood up with the Eleven, raised his voice and addressed the crowd: "Fellow Jews and all of you who live in Jerusalem, let me explain this to you; listen carefully to what I say. These people are not drunk, as you suppose. It's only nine in the morning! Acts 2: 14-15

Let's face it. These people weren't speaking multiple languages at once. They weren't communicating a la the United Nations with headsets and translators. They were bronze-aged desert dwellers; life was brutal. Of course they drank in the morning. Peter, don't be a buzz kill; embrace it and grab a mimosa.

The disciples learn to speak in tongues; and thus, generations of yammering fools are born.

They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them. Acts 2: 3-4

If you've never, in person, witnessed people speak in tongues (or what's better described as grown men and women babbling gibberish under the assumption that the creator of the universe somehow gives a shit enough to control their voice-box), then you truly haven't lived. It's awesome!