You can fetch data from a Twitter user using the PeerReach API with Ruby and Thor. You'll need to subscribe to their API, then use a gem like Excon to make HTTP requests to the API endpoints. The `fetch` method is used to retrieve data from a specific user, and it returns the response in JSON format. The `username` method takes a username as an argument, fetches the data using the `fetch` method, and prints out the relevant information in a human-readable format. The program also includes options for fetching the data in JSON format or exiting with a non-zero status code if the user is not found.