By interacting with the icon at the right of the task bar in the Computer World, the player can enter a small room where it's possible to choose between some few Menu Themes, which change the dessign of the menu frame, as well as the color scheme of the Computer World UI, the wallpaper of the Computer World desktop and the save screen theme.
As of v0.11, there are 12 selectable menu themes in the game, with 2 which are unlocked by default and 10 that can be obtained by progressing in the game.
In the table below is a list of each Menu Theme in order according to the computer menu, along with a short description of it's obtaining conditions.
| Preview | Condition(s) | Matching Desktop | In-game |
 |
Default menu theme |  |
 |
 |
Unlocked by default |  |
 |
 |
Obtain 10 or more feats |  |
 |
 |
Obtain the Clockworker effect |  |
 |
 |
Heal the injured patient in the Hospital |  |
 |
 |
Obtain 20 or more feats |  |
 |
 |
Obtain 30 or more feats |  |
 |
 |
Collect all 7 Crystals |  |
 |
 |
Get at least 3333 N (Money) |  |
 |
 |
Achieve 100% Music Completion Rate |  |
 |
 |
Achieve 100% Music Completion Rate |  |
 |
 |
Achieve 100% Music Completion Rate |  |
 |
Trivia
- Menu Theme 5 references the game 311, also made by Jojogape. The menu theme itself, the sound effects it uses (being the only menu theme in the game to change the menu SE before v0.11 implemented menu themes 10 and 11) and the matching wallpaper in the Computer World are all assets used originally in said game.
- Menu Theme 8 was implemented in v0.10, as the Crystal collectibles didn't exist beforehand.
- The matching desktop background for Menu Type 6 is the grid background used for the exterior of the Dance Flood, and the matching desktop background for Menu Theme 8 is a frame of the rainbow fish of the Flying Tuna event.
- Prior to v0.10, the theme changing room didn't exist, instead menu themes were automatically switched by interacting with the icon at the right of the task bar on the desktop.
- Menu themes 9-12 were added in 0.11, and 10-12 require 100% Music Completion Rate.
- Theme 9 uses the last value for the variable defining which theme is currently used, implying that it may have been the last theme to have been created.
- Theme 10 is, similar to 5, based on a game Jojogape previously made. The game in question is a puzzle game named Spotlight Waltz. It also has its own sound effects, and the wallpaper is a screenshot from the game with a blur effect and slight tilt.
- Theme 11 is, very clearly, a reference to ZApNeF, Someday's minigame, with it's own unique sounds and the matching wallpaper being a 3D render of one of the game's stages.
- Theme 12 and its save theme were originally made for nulsdodage's Korean translation of the game. Before debuting in Someday, this theme was first introduced in the fangame Yume 2kki as the Theme 40, albeit using a different color for the background and a different set of numbers. This theme also has a variant left in the files of the version 0.11 of Someday, unused.
- Its appearance may reference the Mall.