Always an awkward moment when taking off.
Tower: "Cessna 123 Hotel, cleared for takeoff, runway 34."
Cessna: "Cessna 123 Hotel, cleared for takeoff, runway 34."
(45 seconds later)
Tower: "Ah, Cessna 123 Hotel, not getting transponder information from you."
Cessna: (swearing inside cockpit, then over the radio) "Cessna 123 Hotel, just recycled transponder, how's that?" (when 'recycled' actually means 'turned on because he forgot'
Tower: "Positive radar contact, Cessna 123 Hotel."
Speaking completely theoretically.