The best album packaging gives artists the opportunity to enhance the story told throughout their music or tell a new one entirely — and all the artists on our list of Album Cover Easter Eggs took full advantage of the medium.

Several of the albums covers on this list — such as Rush and Iron Maiden — are self-referential, giving longtime fans plenty of sight gags and inside jokes to discover. Others include references to different artists, although the exact meaning of these nods isn’t always clear. (You’ll see what we mean when you get to the Nirvana entry.)

Some artists used their album artwork as a way to address their current status. Harry Nilsson and John Lennon poked fun at their naughty reputation on the cover of Nilsson’s Pussy Cats, while Led Zeppelin may have inspired — intentionally or otherwise — more chatter about their alleged occult dabblings.

While some of the album cover Easter eggs on our list are lighthearted and irreverent, others carried a sense of gravitas that underscored the magnitude of their albums. When David Bowie released his swan song, Blackstar, two days before his death, it became clear to fans that he used his music as a vessel to usher him from one plane to another — and he used the packaging of his final album to convey a poignant message about mortality.

Read about all of these examples and more in our below list of Album Cover Easter Eggs.