Yes the dialogue is custom - Imgflip

Dialogue That Might Play When You Fight Sans by ItsWolven on DeviantArt

UNDERTALE] sans dialogue sprites by SooSSpy on DeviantArt

Custom Dialogue) Why is Papyrus so mad?: Undertale Undertale funny, Undertale comic funny, Undertale

UNDERTALE – Sans Boss Dialogue

GitHub - ElCholoGamer/undertale-dialogues: A rest API for generating Undertale dialogue boxes.

spacialesbian — Just noticed something about Sans' after-fight

Undertale Sans fight. Entire dialogue with Flowey. No deaths

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…

HS!Outerhorror by HorrorswapSans - Game Jolt

Flawless Boss Battle - Undertale Genocide Final Boss (Dialogue Emphasized) on Make a GIF