Pause the game while playing it, then enter any of the codes below at the "Secrets" option. Certain codes will only work in certain levels though.

Effect Code
Shoot beams temporarily -- GazerBeam
Destroy all nearby enemies and items -- SmartBomb
Level select -- SpringBreak
Faster game -- SassMode
Refill 25% health -- UUDDLRLRBAS
Health remains constant -- PinkSlip
Temporary unlimited Incredi-points -- Showtime
Superspeed Incredi-power while running -- DanielTheFlash
Temporary unlimited Incredi-power while playing as -- Dash DashLikes
Fast Running and Ramming Incredi-power -- McTravis
Findtrails and Superpunch -- Kronos
Fire Trail -- AthletesFoot
Unlimited Elastigirl powers -- Flexible
Dash not hurt when running into objects -- Gilgendash
Temporary unlimited Incredi-power while playing as Violet -- TonyLoaf
Slow motion player -- BWTheMovie
Horizontal camera control switched -- InvertCameraX
Vertical camera control switched -- InvertCameraY
Big head mode -- Einsteinium
Small head mode -- DeEvolve
Toggle HUD -- bHUD
Reverse movement with Nomansian Island turret -- InvertTurret
Some objects flash different colors -- DiscoRules
Brightness/bright colors -- EMode
Introduction sequence -- Hi
Credits sequence -- YourNameInLights
Easier game -- BoaPlace
Henchmen always launch death shrapnel -- Dandruff
Battle mode -- RotAIDalg
Beat levels with Bombvoyage -- Labombe
Deactivate all active codes -- TheDudeAbides