I jump up and down and scream with excitement. Half the time, I don't even realize my reaction until it's too late lol. I get such a rush of happiness knowing Michael is loved and his music is played wherever I go. =)
Last time that happened in public was at a Wendy's. They played "Beat It."
This has also happened at the supermarket where I work. They usually play J5 music though, but I just go nuts whenever they play Michael's solo stuff. They have played "Dont Stop Til You Get Enough", "Rock With You", "Billie Jean" and "Burn This Disco Out." The last time they did this, I had to apologize to my customer for my sudden change of mood lol. xD
It doesn't happen with J5 stuff, though. That just makes me happy because I think of cute little Michael (and not sexy Michael lol.) Yesterday, for example, Michael saved my job. I was so close to snapping at one of my customers, but then "ABC" came on, and I just focused on listening to it instead. Instant mood-lifter, I swear. I was fine after that.