This was the closest Led Zeppelin came to glam rock. It sounded a little like T-Rex and David Bowie, but Zeppelin was not about to put on make up or wear feminine clothes.
The song is about Led Zeppelin's groupies. Robert Plant's vocals are hard to hear because they are buried in the mix.
Led Zeppelin performed this live on their 1975 and 1977 tour dates, and for fun, dressed up in drag one night to perform it.
At the end of this number, a suitably sickly cough arises from John Bonham, whose health was not always in best shape after "A night on the tiles."
In an interview with Rolling Stone (March 13, 1975) the interviewer, Cameron Crowe, commented that Robert Plant seemed to be depressed about the thought of growing up. Plant responded: "Well, I am. I haven't lost my innocence particularly. I'm always ready to pretend I haven't. Yeah, it is a shame in a way. And it's a shame to see these young chicks bungle their lives away in a flurry and rush to compete with what was in the old days the goodtime relationships we had with the GTOs and people like that. When it came to looning, they could give us as much of a looning as we could give them. It's a shame, really. If you listen to 'Sick Again,' a track from Physical Graffiti, the words show I feel a bit sorry for them. 'Clutching pages from your teenage dream in the lobby of the Hotel Paradise/Through the circus of the L.A. queen how fast you learn the downhill slide.' One minute she's 12 and the next minute she's 13 and over the top. Such a shame. They haven't got the style that they had in the old days... way back in '68."
Multiple rock journalists have floated the hypothesis that this song is about a groupie named Lori Maddox. Maddox, whose name is sometimes spelled Mattix and who is sometimes called Lori Lightning, was a teen groupie who supposedly had an affair with Jimmy Page. She was only 14 when the alleged affair started, which would have made the relationship statutory rape. The lines that possibly give away Maddox as the song's subject are:
One day soon you're gonna reach 16
Painted lady in the city of lies
Maddox went to clubs with her friend, a groupie named Sable Starr, who supposedly slept with big-name rockers like Mick Jagger, David Bowie, Iggy Pop, and others. For most of her life Maddox said these encounters were consensual with fond memories, but that tune started to change in her older years as she viewed the situation very differently. She said she'd not wish for other young girls to sleep with grown men and that she sees the abusive aspect of it.
The stigma against sexual relations with younger women wasn't the same in the '60s as it became later in American culture.
Some journalists who have backed this hypothesis are Paul Rees (Robert Plant: A Life) and Mick Wall (When Giants Walked the Earth: A Biography of Led Zeppelin).