Now that's an amusing (and slightly startling) sound. Chara laughs, not bothering to try and keep it quiet. If Frisk is offended by being laughed at, that's too bad for them.

Chara does think over Frisk's suggestion, briefly. It still doesn't explain why Chara revived relatively unscathed... Honestly, they could fill an entire book with the unanswered questions they have at this point.

"Let me propose a new theory:" Chara says, "You just have terrible luck."

And in regards to Frisk's speculating about the Underground, Chara suggests: "Monsters also have terrible luck."