I've been to one of John Barrowman's SDCC panels. They really are something to be seen at least once in your life. It's very clear the man is in his element at this yearly convention.
For a very brief taste of that flavor, here is what Barrowman is wearing to wander around the show. The actor best known for his roles in Dr. Who and Arrow has kept his Kylo Ren cosplay low key, as you can see.
— John Barrowman MBE (@Team_Barrowman) July 21, 2016