The deity huffed before placing his scythe to rest as his day was finally over. He sure had had some fun in his reaper form - a look he rarely used other than to scare people who actually deserved to meet their fate.
“Should I be smiling.”
The question had some geniunity in tone, but the intention was mostly to shoot down smiling or looking anything but ‘dreary' in a place like the Underworld. Thanatos had the better niche out of the two, or at least he did in Charon’s mind. While Charon spent his lifetime and would spend the rest of his lifetime ferrying souls back and forth across the same body of water day in and day out, Thanatos was everywhere, reaping people.
So, perhaps Charon was a little jealous, and perhaps there was hostility in his words.