Terry Pratchett's Guards! Guards!

Guards! Guards! is a comic fantasy novel by Terry Pratchett, part of his beloved Discworld series, adapted for the stage by Stephen Briggs. 
In the corrupt city of Ankh-Morpork, a secret society plots to summon a dragon and install a puppet king—but things go hilariously sideways. Enter the ragtag Night Watch: a cowardly captain, a drunken sergeant, a clueless corporal, and a 6-foot-6 dwarf. As the dragon turns out to have plans of its own, it's up to this unlikely crew to save the city (and possibly themselves) from going up in smoke. A riotous fantasy full of wit, satire, and fire-breathing chaos.