[Sans's perpetual grin quirks up lopsidedly. Yeah, they're sharing more than just emotions, aren't they?] Was thinkin' about the robot cake I made you. Figured that'd be a good test thought. [Better than all the other emotions swirling around this conversation. Better than the numb but sharp edges of Sans's mind.] But hey, I could go for cake.

[But Papyrus knew it was cake-related, and not just some happy thought. Sans's emotion magic doesn't work that way; he can't tell what's making anyone feel things except by the normal methods. Their minds are attached again. He doesn't say it, but he's thinking about it. He can't not think about it.]