Possible Clues:

• Response to 'Look over there!'
• Words from one succeeding at Photo Hunt
• "Yeah, there is a resemblance there"
• Discoverer's call
• Response to pointing out a resemblance between two people
• Op art viewer's cry, maybe
• Spotter's words?
• "Thar she blows!"
• Bird-watcher's cry
• 'Eureka!'