I was in 10th grade, heading to Sao Paulo as an exchange student, about 14 years ago, on Varig. The father of the host family, who travels to the US and Europe frequently on business, called ahead and upgraded me with miles. I didn't know until I arrived at the airport. After check-in we were directed to the lounge (I don't know whether it was a First, or Business Lounge). My parents seemed to enjoy the lounge, though I didn't realize the implication of a First Class ticket, nor did I realize 'everyone' didn't get to go to the lounge.
I remember the cabin as being very, very spacious. When I sat down I was given an amenity kit, and some slippers. They showed movies with a projection TV sitting on the floor of the F cabin in the center. Food was prepared to order. It was GREAT!
Unfortunately, he (perhaps) forgot to call about the return trip to the US, so I was back in Coach in a midle seat. Wow, what a difference. I believe that was the trip that made me the upgrade-hungry traveler I am today.