I saw a hypnotist do a show years ago. She had 2 people on stage. She told the first person that she was from a different planet and had just arrived. The 2nd person was told that they could interpret the alien's language. The 2 people began to have a conversation in a gibberish language. The comedian would ask what did she say. Then the person would reply in English. Then the interpreter was told things to ask the alien. More gibberish, with a gibberish reply. It sounded like what Arabic, Japanese and Portuguese would sound like if you combined all 3.
It was hilarious. Even a bit unbelievable, as if they could have been part of the act. Later I asked the hypnotist if she could hypnotize someone into learning a foreign language. She said NO and added that she could only make them believe that they could speak the language.