Never came close to packing anyone even remotely decent until this year, so I've heard about this happening but never experienced the disappointment.
Had a very minor one with (definitely got excited too early but you know how it is):
Brazilian > LW .... holy **** i've pulled Neymar.... Coutinho
But the bigger one I had, as I was 100% convinced, was:
French > ST > Atletico ..... it's Griez.....Gameiro
I'm sure there's bigger ones out there, what was your "favourite"?