Disrespecting Allah while joking.
Many will say - Brother! This was just for fun.
Fun? With the attributes and qualities of Allah? How dare!!
It is clearly stated in the Quran -
وَہُوَ یُطۡعِمُ وَلَا یُطۡعَمُ
He (provides food for all), does not take food from anyone!
- Surah Al-An'am -14 (fragment)