MUAC
Heard today in Maastricht.
Controller:
BAWxxx, your restricting traffic is is a Kestrel (MYT) 5nm off your right wing 1000ft above. Expect higher in 2 minutes.
Pilot:
Wow, wasn't aware kestrels flew at FL330, we're keeping a good look out.
It had us laughing even if it's not so funny to read!