Complex sentence: The Music Meister officially appears in the episode "Duet", where he puts The Flash into a shared coma with Supergirl, with the pair living inside the plot of a movie musical (leading Barry to nickname the alien the "Music Meister").
Split into simpler sentences: The Music Meister officially appears in the episode "Duet". He puts The Flash into a shared coma with Supergirl, with the pair living inside the plot of a movie musical (leading Barry to nickname the alien the "Music Meister").