The 29-year-old recently played a show at the O2 Academy in Glasgow but he arrived a day early and dropped by the Griffin and Nice 'n' Sleazy bars.
Some of his minders asked the King's Theatre press officer Mark Irwin where they should go and he advised them to visit the bars.
According to UK newspaper Daily Record, Griffin said: 'It was a great night and Brandon spent the evening at the back of Nice 'n' Sleazy watching some of the acoustic bands during an open mic night.
'Some people didn't recognise him because he was clean shaven and wearing a checked shirt and jeans.'