Sullivan made a cameo appearance in Gavin & Stacey broadcast on BBC One on 1 January 2010. Sullivan sang with Jessica Cervi and Sarah O'Connor in the final of RTÉ One's Fame: The Musical in Dublin on 13 June 2010. Sullivan played the lead role of Galileo Figaro in the 2011 UK tour of We Will Rock You. Sullivan took over from Alex Gaumond in the lead role of Galileo in We Will Rock You in the West End Production of the musical at the Dominion Theatre. The role reunited Sullivan with his former Grease co-star, Lauren Samuels, who plays Scaramouche in the show.
