The Prism-gram is a prism-like object that sends mail in the Land of Ooo, and possibly comes from the Crystal Dimension. Once one has written a letter, one swipes the Prism-gram on the paper and it absorbs the writing. The message is transformed into light waves and sent to another Prism-gram via a beam of colored light. Then it converts the letters into brain waves and shoots them onto one's forehead through a similar, laser-like beam. So far, it has only appeared in the season 2 episode "Her Parents," where Jake used it to send a message to Lady Rainicorn's parents, Bob Rainicorn and Ethel Rainicorn. It has also appeared in the season 9 episode "Come Along With Me," the show's finale, in BMO 's cave.
- It seems that it can really hurt once the letter (in the form of a laser) is shot at the forehead.
- The letter Jake wrote means: "To Mr. Rainicorn and Mrs. Rainicorn, Rainroad 47. Please come here one hour early for lunch. I don't have a pet turtle. From Jake." In Korean, it reads: "무지개콘 선생님과 사모님께, 47 무지개 길. 점심에 한시간 일찍 와주세요. 나는 애완 거북이가 없어요. 제이크 드림"
- "Rainroad 47" could be a reference to the Mario Kart series, in which Rainbow Road is a race course.