Step 1: Concept Identification: The query requires identification of a clear instance of an "entertainment event." Such an event is primarily organized for audience amusement and enjoyment.
Step 2: Detailed Analysis:
(1) Celebrity Night: An event designed for entertainment through celebrity performances, appearances, and interactions. Its core purpose is amusement, aligning perfectly with the definition.
(2) Graduation Day: A formal ceremony marking academic achievement. Its primary purpose is celebratory and ceremonial, not entertainment.
(3) MICE: Acronym for Meetings, Incentives, Conferences, and Exhibitions. This refers to a category of business, professional, and educational tourism and event management, not an entertainment event itself.
(4) Birthday Party: A private social gathering for personal celebration. While it can be entertaining, it is classified as a personal/social event rather than a public "entertainment event" within the event management industry.
A celebrity night is the most suitable example of an event whose sole purpose is public entertainment.
Step 3: Conclusion:
A celebrity night stands out as the clearest example of an entertainment event among the provided options.