Joke

A man walks into a bar. 
The barmaid says to him "The usual, sir?" 
He says ".....

No. Actually we can't tell this joke, it sends all sorts of wrong messages. It can't be a man because that is gender specific, so it has to be a person.

OK. A person walks into a bar. 

No. Stop. First of all walking is not PC, as it excludes wheelchair users so we need to replace "walks" with the much more neutral "goes". 

Also the whole bar thing is wrong. It endorses the concept of alcohol consumption.
Let's make it some neutral public place. This is good, because I wasn't sure how we were going to deal with the female barmaid figure anyway.

Clearly the rude double entendre in the original has to be removed for fear that sensibilities are disturbed, so we can replace that with something less controversial, something non specific.

Here we go.

A person goes into a generic public place and has a conversation with an employee. 
A misunderstanding occurs with hilarious results.

I thank you.  See. It's the way that I tell 'em.