Serious Mode
Serious Mode (for lack of an official name) occurs under certain conditions and removes minor jokes while it is in effect. It is entered automatically in certain circumstances.
- When fighting a Boss Monster (Toriel, Asgore, or Asriel).
- With Asgore, the Serious Mode flag is not always cleared properly, and may persist if the protagonist dies or quits.
- During the Genocide Route-exclusive fights against Sans and Undyne the Undying.
- Items with comically shortened titles in encounters are abbreviated in a less humorous way.
| Name | Usually shortened to | Becomes |
|---|---|---|
| Spider Donut | SpidrDont | SpdrDonut |
| Spider Cider | SpidrCidr | SpdrCider |
| Butterscotch Pie | ButtsPie | Pie |
| Tough Glove | TuffGlove | Glove |
| Manly Bandanna | Mandanna | Bandanna |
| Unisicle | Unisicle | Popsicle (use text stays the same) |
| Cinnamon Bunny | CinnaBun | C.Bun |
| Abandoned Quiche | Ab Quiche | Quiche |
| Ballet Shoes | BallShoes | Shoes |
| Old Tutu | Old Tutu | Tutu |
| Annoying Dog | Annoy Dog | Dog |
| Dog Residue | DogResidu | D.Residue |
| Astronaut Food | AstroFood | Astr.Food |
| Instant Noodles | InstaNood | I.Noodles |
| Glamburger | GlamBurg | G.Burger |
| Legendary Hero | Leg.Hero | L.Hero |
| Torn Notebook | TornNotbo | Notebook |
| Cloudy Glasses | ClodGlass | Glasses |
| Stained Apron | StainApro | Apron |
| Worn Dagger | WornDG | W.Dagger |
| Heart Locket |  <--Locket |
H.Locket |
| Undyne's Letter | UndynLetr | Letter |
| Undyne's Letter EX | UndynLtrX | Letter |
| Popato Chisps | PT Chisps | Chips |
| Mystery Key | MystryKey | Key |
| Steak in the Shape of Mettaton's Face | FaceSteak (Fsteak) | Steak |
| Hush Puppy | HushPupe | HushPuppy |
| Temmie Armor | Temmie AR | Tem.Armor |
- Instant Noodles displays a short use text (being eaten dry) and recovers 90 HP instead of displaying pages of use text (being cooked for a long time) and recovering 4 HP.
- Spider Donut's "Don't worry, Spider didn't." alternate use text will not appear.
- The following items do not make sounds when eaten:
Unused items that had their normal abbreviations changed to something less humorous.
| Name | Usually shortened to | Becomes |
|---|---|---|
| Pumpkin Rings | PunkRings | PmknRings |
| Stoic Onion | StocOnoin | Onion |
| Ghost Fruit | GhostFrut | GhstFruit |
| Puppydough Icecream | PDIceCram | Ice Cream (use text stays the same) |
- Dog Residue is the only item that makes a sound when used in this mode.