Hilbert's Grand Hotel paradox, the one about the hotel with infinitely many rooms, I'm not very good at explaining it... but it's about the fact that with infinitely many numbers, we always have n+1.

I think it also has the bus with infinitely many seats; if you take 2n people, there will always be an odd-numbered seat available for each new passenger.

Wow, I've really gotten myself all tangled up, hahaha. Since you're a mathematician, I'm sure you can explain it better than I can.