Had Mario not said the puddle was indeed water, Brain would have genuinely assumed it was weird ice. What's one more weird thing to add to the state of the Ship, really. But Mario's right... ice does not normally look like that.

Brain's face scrunches a bit in confusion. Was he just not looking at it right? Is he really that tired that it didn't ripple? He squats down and touches it to confirm his troubles. And yeah okay that's some weird stuff. He saw maybe one or two wet floor signs the day before when stopping by the Cafeteria for a meal, but he hadn't deigned to question them! Why would he? They were just puddles!

"What the hell?" He mutters before looking back up at his friend, who still doesn't look any better. Brain bites the side of his mouth as he thinks more, but absentmindedly asks again: "You okay?"

Brain's never seen Mario's so shaken up over something. Maybe briefly, when talking about the planet they're on, but not like this.