Do you have any stories of very senior leaders surprising troops to cheer them up?

Not in the "Very Senior" category, but my first Squadron Commander would show up on the crappy posts occasionally and relieve the one or two striper posted there for the shift. One of the more popular stories was when he took over a Close in Sentry post on an aircraft and the pilot came out, had his line badge checked and our commander advised the pilot it was ok to proceed. The pilot asked him what about a salute, assuming he was dealing with an enlisted type, and our commander said he was waiting for one. The pilot was a 1st LT and our commander was a Major.

Great shot of GEN George Casey right there!
I always remember our wing commander popping into various squadrons unannounced to recognize a team member for outstanding performance. Everyone would come out into an open bay for 2 mins while he praised the Airman. A quick coin & pat on the back went a long way with everyone.