I pick Jimmy as the prankster and the Chief as the prank-ee. My April Fool's submission (with my apologies to the younger generation who may not understand the prank):
Jimmy knew he was in serious trouble. No. Make that SERIOUS trouble. He'd been planning to get the Chief all month and, well, things just went wrong and ... wronger. He'd heard that the launch of EPRAD's polar mapping satellite would pass over Metropolis just as it went out of the atmosphere. As it happened, there was a M*A*S*H marathon on shortly afterward. Inspiration struck and one thing led to another. One of his Dad's friends had even loaned him a pair of high-powered binoculars for the occasion.
He'd been feeding the Chief information on the satellite's mission, goals, instruments, personnel and anything else he could think of for a week. It was a noon liftoff and his window of opportunity was launch plus 3 minutes. The monitors in the bullpen were on and tuned to the EPRAD broadcast. Perry's response was an appropriate mixture of tolerance and interest. He was pretty sure he'd played his hand right.
All morning everything was going well. Just after the rocket launched was when things started to go south. When Superman flew in the window carrying Lois, Jimmy forgot all about the prank. She'd been out following up on a big story and apparently had another front page in her near future. Whatever the situation had been, she was smiling now and thanking Superman for her latest rescue. Superman seemed to be in good spirits and was greeting people he knew in the newsroom rather than flying off immediately.
That's how it happened that Superman was talking to Jimmy when the EPRAD announcer broke the mood. The explosive bolts to release the second stage booster hadn't fired properly and separation hadn't occurred. If the backups weren't able to fire then atmospheric drag would cause the rocket to crash in one of the most densely populated parts of Europe.
Jimmy had turned his attention to the EPRAD broadcast when Superman asked, "Can I borrow those?"
Superman repeated, "Jimmy, can I borrow your binoculars? I need a little more detail to see whether I have a satellite to chase down or not."
"What? Oh, sure. Here." Superman stepped to the window, looked through the binoculars and the deed was done. "Thanks," was all he said as he handed the binoculars back. Then Clark flew out the window in his Superman suit.
Jimmy was pretty sure that he was the only one who had seen until he heard Mad Dog Lane explode behind him. "YOU!!! YOU RAT! You dirty lowlife rotten stinking RAT!"
Yep. SERIOUS trouble.