Heard this during the FedEx rush at IND this evening. Because IND was busy at the time, some of what occured was cut out.
The first audio you hear is a controller giving FDX24 initial instructions after checking on. FDX1624, who had checked on about 5 minutes earlier and was given descend to 7000 and direct VHP, answers for him thinking that the controller was dropping the 16, as most of the FDX flights coming in at night are in the 1600's.
Was a confusing situation for a minute, but the controller and pilot of 1624 lightened the mood a bit.