Possible Clues:

• Greeting to a parent
• Mugger's cliché
• Handmade sign held up by a kid in the bleachers
• Greeting often heard on the second Sunday in May
• Phrase spoken while waving at a TV camera
• Shout-out from a sideline player
• Athlete’s TV shout-out
• Fan's words to a TV camera, perhaps
• Game show shout-out
• Shout-out from the stands