Michael Schneider Variety Editor at Large SPOILER ALERT: Do not read ahead if you have not watched Season 10, Episode 5 of “The Masked Singer,” “A Celebration of Elton John,” which aired Oct. 18 on Fox. Elton John and Bernie Taupin wrote the track “Philadelphia Freedom” in 1975 at the behest of tennis icon Billie Jean King (whose team was the Philadelphia Freedoms). So, it was wildly appropriate that King performed the song on Wednesday during “A Celebration of Elton John” on Fox’s “The Masked Singer.” King performed “Philadelphia Freedom” as the Royal Hen — and the fact that we know she was on the show means that, alas, she was also the next celebrity to be unmasked on “Singer.” “A true trail blazer, she is famous for championing equal opportunities for all, and has made it her royal mission to be a voice for the voiceless,” a “Masked Singer” voiceover shared in giving the hints to whom the Royal Hen might be.