I had a weird one a few weeks ago. Booked in D LHR-BKK, loadsheet was F6 J9 W0 Y0. I asked at check-in about paying for an airport upgrade, and was first told "no, it's oversold at the back but J's fine" cue long, chatty phonecall from check-in agent to a yield manager to muse about offering it to me, before deciding "no, speak to ticketing".
So I spoke to ticketing who tried to upsell me a re-fare to Full F (until I explained what A class was), and in the end we all agreed £10k seemed a touch steep.
At the gate I got the red light, and instead of "U/G Due to DUT Entitlement" (which is standard for OpUps), my new BP read "U/G Due to Staf Entitlement" (sic)
So what happened there??