Bob is holding it in.

Lex: Hey Bob what are you up to?

Bob: Nothing just sitting here holding my shit, because I don't want to go to the toilet. 

Lex: What? Why not?

Bob: I don't feel like it. 

Lex: okaaay!! p.p

Bob: Oh what the hell, I give up. Shit wins I am going to the toilet.
-Bob leaves to the toilet-

Lex answers, Why are farts funny?

Lex: I came up with an Idea.
It goes like this, I will get in the elevator with my boss and a bunch of people and wait till my boss clicks on the 10th floor, then I will click on the 5th floor and when the door opens for me to leave I will release a silent fart in the elevator and leave my boss to rot till the 10th floor.

Bob: haha why are farts funny?

Lex: I think that might have to do with the fact that they are generated by clapping the asshole without using the muscles and simply depending on the high air pressure released from the ass hole.