Yes the dialogue is custom - Imgflip

Undertale - Sans Boss Fight

UNDERTALE 5th Anniversary Alarm Clock Winter Dialogue - Sans

CP) Sans as Shane Mod and New Dialogue at Stardew Valley Nexus - Mods and community

Today is let sans rest day! So I thought I'd take some inspiration from the undertale clock dialogue. I know it's a bit lazy to just draw…

entree mysite

nothing useful. — Why doesn't sans use any of his crazy attacks

Pixilart - Sans Genocide Dialog by 3DaMIR

Undertale Genocide run explained: How to play the game in the most evil way possible

AU where everything is the same, except Sans' dialogue just before you fight him is the same as Dr. Andonuts' from Halloween Hack., Undertale

Undertale AU] Inverted Fate - Sans Fight by TheCakeOfTruth_ - Game Jolt