Possible Clues:

• 'Not on ___!'
• "Not on ___!"
• On ___ (how pranks may be done)
• “Not on ___!” (“Forget it!”)
• 'Not on --!'
• 'Not on ___!' ('Never gonna happen!')
• "Is that __?": challenging words
• On ___ (how some pranks are done)
• On ___ (by challenge)
• On __: if challenged