Ghost Smile D.I.Y. features a good deal of customization. The player can choose many details when customizing his or her main character:
The player starts out with the basic 3D RPG battlefield. Enemies can be placed wherever the player wishes. There is a texture and model editor, allowing the player to create completely original levels and battlefields. If the player's memory card contains Rock Band or Rock Band 2, he or she can include the songs in both of those games in the soundtrack of the custom level being created.
After creating ten levels, the player accesses a series of animated cutscenes in which the protagonists of Ghost Smile 3 give interviews to an unseen character about their experiences during the events of the game:
The first interview reveals information about the events of the game from the perspective of a new character, Kurt, a Ghostpunk. Kurt wears a T-shirt with the Avenged Sevenfold skull-bat, and exhibits a rebellious and "indie" attitude. He tells the interviewer about how he and Smile fought a pair of Mythic's minions inside an underground subway station. Kurt then reveals a bit about himself: He was named after Nirvana frontman Kurt Cobain, and was raised by "cool punk rock parents". He and his parents were killed by one of Mythic's human minions. Kurt's parents, having fulfilled their destiny, went to Heaven, though Kurt himself remained as a ghost. His destiny was to make some really good music, which he quickly fulfilled, but he decided to stay as a ghost until he could avenge his parents and defeat Mythic. He became obsessed with achieving this goal, remaining as a ghost for several thousand years. Far into the future, he was present when Mythic stole a recently-invented time machine, known as the Time Capsule, from the Greys. He hitched a ride as Mythic escaped into the past with the machine. He landed in the present day, quickly making an ally of Smile, who became one of his closest friends and joined him on his quest to defeat Mythic. After recounting this story, he breaks the fourth wall and tells the interviewer "You know what, just play the frigging game", and drives away in a silver pickup truck with a Radiohead bear bumper sticker.
The next interview reveals yet another new character, Morris the Specter. Morris is an extremely honorable and powerful ghost. During the interview, he reveals that he is a ghost because his destiny in life was to become Smile's trusted right-hand man and to save hundreds of lives, but as Smile died at birth, Morris could not fulfill his destiny. Therefore he voluntarily remained as a ghost to assist Smile and fulfill his destiny. He concludes by telling the interviewer that he will stick around for a little while to make sure things work out, but will probably ascend to Heaven sometime soon now that he has achieved his destiny.
The third new protagonist is introduced in this interview. His name is Mart, a Grey who became a ghost after starving to death during the Great Depression. Throughout the interview, he attempts to sell various inane objects to the interviewer, including a leaf that happened to be lying on the ground ("It's a very special leaf! I inherited it from my grandmother!). Mart, despite being a Grey, is tinted blue, with tentacles, something also unique. Mart is something of a trickster, making dryly sarcastic remarks. He claims that his salesman personality has actually decreased since his adventure with Smile, and that he now knows that people are more important than money (before promptly trying to sell the interviewer to a passerby).
Isabella, first introduced as Smile's mortal wife in Ghost Smile: 2nd Chance, returns here. She summarily refuses to tell the interviewer anything, saying that she and Smile deserve some privacy.
The last interview is of Smile himself. He is friendly, outgoing, and something of a bookworm (as indicated by the massive stack of books sitting next to him). He tells the interviewer that Mythic is dead, and that there is nothing to fear anymore. Due to his tampering with history during the course of the adventure, time is slowly reverting to the way it would have been if Mythic had never existed and if he (Smile) had survived birth. Smile observes his arm, which has become vaguely human in the past few minutes. He grins, saying that time is almost fixed, and walks away.
The interviewer presents footage of the interviews to an unseen figure, who tells him he's done well, and that Smile isn't going to find his peaceful mortal life as relaxing as he thinks...