The following groups of people are typically invited to the System Demo:
Customers. Especially those who have an interest in the specific items being demonstrated. We want to get immediate feedback to ensure we are heading in the right direction.
Organizational stakeholders. This includes business owners, others representing the business, sponsors, functional areas in the organization (such as security, sales, marketing, etc.), organization management, and other interested parties.
The train. It is obvious that people involved in the System Demo would be invited. What might not be so obvious is that everyone on the train should also be invited. This allows people to understand what else is happening on the train; you never know what people will find useful. More importantly it helps develop the understanding that we are all part of the train and that we are collectively responsible for delivering on train commitments.