Your instructor pool could be very specific (only faculty, never faculty, only students) or could be broader and include the entire campus and off-campus community, including alumni. Broadening your instructor pool can be a great way to engage the community.
=== Who is Your Target Audience? <br/> ===
Some pop-ups are targeted only to students and in some cases a subset of students (e.g., undergraduates in particular majors). Some can be developed for other specialized audiences (segments of alumni, faculty or the community). Alternatively, you can open up a pop-up to everyone, encouraging the mixing of backgrounds. You can also leave it up to the instructor to identify the audience.