Joke

A too-serious day... time for a joke.

joke (n)
ihlaya, amahlaya

joke (v/i)
-ncokola; -dlala (play) also
-ntela; -tekula; -soma

So, lots of ways to say 'you must be joking!'
for example
"Mhlawumbe uyadlala!"
(direct translation: perhaps you're playing/joking)

Now, all we need is a joke in isiZulu. Found this one on the isizulu.net forum, complete with translation (doesn't quite smell of roses, but that is the nature of most jokes).

PS On further reflection, I've wondereed whether to include it. It is crude, painful, and also funny, as are many jokes, across many cultures. Perhaps not for very sensitive readers. But it's part of us, a response to our world, and full of fantastically useful phrases :)

Incwadi ka thisha:
letter from the teacher:

Mzali othandekayo,
Dearest parent,

Sekungaphezu kwamandla ami! Safa iphunga, geza ingane bo! 
It's beyond my control! we are dying of the smell, wash your child!

Yimina ozithobayo,
yours sincerely,

uThisha.
the teacher.

Impendulo ka Mzali:
response from the parent:

Thisha othandekayo,
dearest teacher,

Fundisa ingane... Musa ukuyinuka, mhlathikanyoko!
teach the child... don't smell him/her, your mother's jaw!

Ngenzela nina ngoba nithandana nezingane zesikole, ukuthi ningasondeli kuyona, Zinja!
I'm doing this, since you guys date school children, so that you don't come close to him/her, dogs!

Ngokuzithoba,
sincerely,

uMzali
the parent

Mhlatikanyoko/your mother's jaw seems particularly intense - that one I'd use with care.

https://isizulu.net/
forum
https://zu.oxforddictionaries.com/