Mark is actually a Disney CM that has worked in plenty of other tapings but just as a crowd warmer

he worked at Comedy Warehouse at Pleasure Island, the guy who warmed up the audience before AIE, he travels and does warm up for SW Celebration and
D23 and Comic Con. Each year that Nick Cannon was the host he would come out and start the trend #notnickcannon

Are you sure he's the host? I heard it was Nick Cannon again and that they changed the dates top accommodate his schedule
EDIT TO ADD: Yeah Mark is just the warm up guy not the host, Banks Lee from Attractions Magazine has been there every year and he just told me that Mark is not the host.