Adam had one of the best bookcases, mainly because it held a great secret.

One of the most memorable symbols of He-Man and the Masters of the Universe. Created from the very heart of Castle Grayskull and imbued with the forces of the ancients who once dwelt bodily within its walls at a very different time. The Sword of Power, used to channel Grayskull's magic, enabling the prince of Eternia to transform into the most powerful man in the universe. So where did Adam hide his sword when he went to bed?

Paul Dini was a big fan of comic books in his childhood. And just like something out of a Batman comic, he created a hiding place for Adam's sword. In the past, no other writer had touched upon the issue of needing the sword to be hidden at night. Paul knew that the Sword of Power was very valuable. Thus he created the sliding bookcase mechanism, which suppressed an alcove containing the sword.

MU43 - "The Mystery of Man-E-Faces"
The first time we see the bookcase mechanism is in this particular episode. In a very comical scene Zoar arrives at the Royal Palace to ask Adam to aid in the Widgets. Cringer pleads, "Adam I need my beauty sleep." But by the time Zoar has warned Adam, he is already walking over to the bookcase. Then for the first time we see where Adam's sword is stored. To cut costs of reanimating Adam holding aloft the sword in his nightclothes, the director cuts to a shot of the window, as we can see the transformation taking place.

MU92 - The Littlest Giant
In an almost identical scene to "The Mystery of Man-E-Faces" Adam is once again alerted to the aid of the Widgets, this time by their signal flare. The director uses the same shot of Cringer pleading, this time the dialogue is different, "Adam can't it wait until morning?" Again the exact same animation is used as Adam presses the button, which causes the bookcase to slide along revealing the Sword of Power.

MU125 - "Bargain With Evil" *
Unlike the previous occasions, Adam is in his more familiar clothing this time around. What this means is that, for some reason, he did not carry the sword around during the first few minutes of the episode. The animation is slightly strange here, because as Adam grabs the very small looking sword, by the time he has it across his chest, it is at the more familiar size.