If this clip doesn't do it for you, there is no hope. It's been around since 2010, so it isn't new by any means, but I like it.
Just a little background:
Journey of Faith performed a Christmas "Flash Mob" at the South Bay Galleria in Redondo Beach on December 18, much to the delight of local shoppers. Thanks to all who participated. Merry Christmas everyone!!Journey of Faith can be found here.
If I were so lucky to witness such an event, singing along would definitely occur. Probably at a lower volume, as not to deter other's experience of the event, if you know what I mean and I think that you do.
H/T Ant Gail