The Ice King's tapes are Ice King's video diary. He calls them secret and even evil at the beginning of the episode "Holly Jolly Secrets Part I." The tapes were watched by Finn and Jake on BMO throughout the episodes "Holly Jolly Secrets Part I" and "Holly Jolly Secrets Part II." Jake found the tapes in a suitcase at the dump, and Finn and Jake decide to watch the tapes, hoping to find out some of the Ice King's evil secrets.
The first tape starts off with Ice King explaining his "innermost secrets" but ends when Gunter interrupts him. Ice King then puts on a play, with Gunter playing Ice King and Ice King playing Princess Bubblegum.
The next tape consists of Ice King hosting a Penguin Dance Party.
The third tape starts with Ice King explaining his feelings, and Finn and Jake fast forward though the majority of the tape. When they play the tape again, Ice King is in the middle of explaining how Finn and Jake stopped him when he kidnapped Turtle Princess. He then continues to talk about his feelings, and Finn decides to fast forward the tape again. The Ice King continues to talk about his feelings and soon begins to work out. Finn continues to fast forward till the end of the tape, and Finn and Jake conclude that the tapes are in a secret code.
The fourth tape just consists of Ice King crying in the corner. In the fifth tape, the Ice King pretends to be a newscaster and tries to use the kidnapped Wildberry Princess as an on-site witness.
The last tape shown is of the Ice King over 1000 years ago before the Mushroom War. In this tape, he is still human, and he introduces himself as Simon Petrikov. This tape reveals who the Ice King used to be and how he became the Ice King.
The tapes are seen with analog static but no other artifacts, so the tapes are possibly D-VHS format. The tapes are in a digital format as BMO can output digital video from D-VHS and fast-forward with sound unlike standard VCRs. The tapes were placed in a brown suitcase.