Act to Flirt: Undertale – Flirt your way to Victory

Act to Flirt is a role-playing fan concept built around the ACT command system from Undertale, where players choose flirting as a non-combat option to spare or change the outcome of an encounter. The mechanic lives inside the wider Undertale AU community, where fans expand on the original game’s pacifist philosophy with new characters, dialogue trees, and romantic interactions.

The idea borrows directly from Toby Fox’s 2015 indie hit. In the base game, players can flirt with almost any monster through the ACT menu. Fan creators took that small detail and ran with it—turning a throwaway joke into entire AU storylines.

How the Flirt Mechanic Works

Selecting Flirt during an encounter triggers a unique line of dialogue tied to the specific monster you’re facing. Some react with confusion. Others get flustered. A few are completely unfazed. The response depends on the character, and that’s part of the appeal.

Flirting doesn’t end the fight on its own. You still need to spare the enemy through the Mercy option once their attitude shifts. Think of it as one tool among several—Compliment, Joke, Pet, and so on—that nudges the encounter toward a peaceful resolution.

Why Players Engage With It

There’s a reason this small feature spawned an entire fandom branch. Flirting reveals personality. A monster you’d otherwise just fight suddenly has a reaction, a quirk, maybe even backstory hinted at through a single line.

And it’s funny. The writing leans into awkwardness rather than romance, which lands better than a straight-faced approach would. That tone is what fan creators try to capture in their own AU work.

Common AU Variations

Different Undertale AUs handle the flirt option in their own way. Underfell makes it tense and risky. Underswap flips character personalities, so the same line lands completely differently. Storyshift reassigns roles, meaning the character you’re flirting with might be someone else entirely in another route.

Some fan projects expand the mechanic into a full dating-sim layer. Others keep it as a single line gag, matching the original game’s restraint.

Tips for Players Trying the Flirt Route

Save before testing flirt dialogue on bosses—reactions can be one-time only. Pay attention to the yellow name color, which signals a monster is ready to spare. Mix flirting with other ACT options if a single approach isn’t working. Some encounters need a specific sequence.

Worth noting: not every monster has a flirt reaction. A few will just ignore you, which is its own kind of reaction.

Game Controls

• Arrow Keys or WASD – Navigate menus and move during bullet sequences
• Z or Enter – Confirm selection
• X or Shift – Cancel or back out
• C or Ctrl – Open menu
• F4 – Toggle fullscreen

Credits:

Made by zirkkun

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