VIDEO : 'Jeopardy' Included Question About 'The Flash' & 'Supergirl' Crossover

Unable to play video. Neither flash nor html5 is supported! The Flash and Supergirl's musical crossover delighted plenty of Arrowverse fans when it first debuted earlier this year. The iconic quiz show featured a question about the musical crossover, "Duet", in their December 21st episode. If the non-musical crossovers are more your speed, The CW is providing a chance to revisit the newest one, when it will re-air all four portions of "Crisis on Earth-X" on January 8th and 9th.