I remember a post saying the most unrealistic part of Top Gun is that they all generally have cool call-signs, the only realistic one was Hang Man for leaving his wing men out to dry.

Usually the call-sign comes about from something embarrassing and is given by your wing mates, some of the examples I can remember:

• Legend - definitely badass sounding. But earned by being the first & only pilot to fail some test in the Air Force.
• Zeus - Zero Effort Unless Supervised. Apparently lied to his commander about a report being done, was asked to pull it up, and then the commander stood over his shoulder for the next half hour until the report was done.
• Bambi - during takeoff or landing a pregnant deer jumped in front of his plane, and he meat crayoned it across the tarmac.
• Obi-2: Ewan McGregor played Obi-Wan Kenobi. And his brother was a pilot in the RAF, hence Obi-2. This is a bit unproven but I like to believe.

So I'd imagine the pilot that missed the balloon might be getting a new call sign.