じょうだんです・jōdan desu = I'm kidding/I'm joking
You can use this to say:
- You know I'm just kidding, right?
- Are you kidding me?
EXAMPLES
kidding/joking (cannot believe)

たからくじ で ひゃくまんえん あたったよ!
(Takarakuji de hyakuman en atatta yo.]
(Takarakuji de hyakuman en atatta yo.]
じょうだんでしょ?
(Jōdan desho?)
(Jōdan desho?)

Kidding/joking (ridiculous/no way)

あした、てすとだって!
(Asita, tesuto datte!)
(Asita, tesuto datte!)
ええええ!?じょうだんでしょ?
(Eeeeee!? Jōdan desho?)
(Eeeeee!? Jōdan desho?)

A tip
When you want to deny what you just said, you might be able to get away by saying "Jōdan desu."
When your joke is too much/ridiculous, you might hear "じょうだん きつい!(Jōdan kitui!!)" which means "that's too much."
Let's learn Japanese!