Operetta fans can die happy now that the Savoyaires have "re-created" Gilbert and Sullivan's first collaboration. Only two of Sullivan's songs survived the original 1871 production of Thespis, but in 1982 Kingsley Day composed a score as faithful as he could make it, now lavishly arranged for 25-piece orchestra. The result is as exhilarating as if the music had been recovered. Though Gilbert's plot is light on incident and silly even for a Savoy opera, it's vintage topsy-turvy: inspired by Orpheus in the Underworld, Offenbach's spoof of classical mythology, it traces the calamities that ensue when a troupe of temperamental actors replaces the aging gods of Olympus. Wasting no time on logic or psychology, Terry McCabe's witty staging honors the 14 musical numbers, each a cunning blend of Sullivan-esque sweetness and Gilbertian tartness. Among many charming performances, Julia Hathaway's Mercury scintillates. Through 10/10: Fri-Sat 7:30 PM, Sun 3 PM. Chute Middle School auditorium, 1400 Oakton, Evanston, 847-251-8767. $5-$20.