Oh, that warmth and light were because Strange is part-fire now. No wonder! And, given what monsters are like, it's not alarming. It's certainly not any more unexpected than Sans gaining extra arms, or whatever happened to Gongenzaka after his egg time.

So Papyrus finishes gathering things before coming out, just in time to see Steven dump water all over Strange.

"Oh my god!" He dashes forward, towel at the ready, and drops it on the man. The towel should soak up egg goop, water, and mud alike. Hopefully it's not too flammable.

"...I don't know if I should be alarmed! Strange, does the fire hurt?"