C'est quoi le rapport ?

6. C'est quoi le rapport ?
pronounced more or less: say kwah luh rah-porh ?
Literal translation: "It's what the connection?"
Variants:
1. Je ne vois pas le rapport. / Je vois pas le rapport. = I don't see the connection (I don't see what that's got to do with it).
2. Il n'y a aucun rapport. / Aucun rapport. / Ça n'a aucun rapport. = There's connection whatsoever. / That has nothing to do with it.
Implications: C'est quoi le rapport? is the equivalent of these American English expressions: "What's the connection?" ; "Where's the connection?" and sometimes "What's your point?" Most especially, when accompanied by a scrunched-up face of unabashed disdain, it's the equivalent of: "What's that (expletive) got to do with it?" The speaker clearly finds the remark just expressed off-base, unrelated to the topic at hand. It is unlikely that s/he is actually inviting you to explain the connection. You're going to have to insist like crazy if you want to clarify your point, because it's already been discarded and possibly you along with it.
Remarks: 
1) These expressions are also entirely valid ways of sincerely asking someone to connect the dots. Any implication of judgmental exasperation comes from context and/or tone of voice.
2) C'est quoi le rapport? is familiar French. Its variants are appropriate in any context.

Example One: You're chatting in French with family members and a couple of their friends. One person keeps tossing in inconsequential tidbits -- asides that have nothing to do with the conversation, as if she were playing for points in an imaginary game of "how many useless comments can you come up with in 30 minutes to show off how much time you spend reading Wikipédia?" The musicians at the table start talking about performing their own stuff versus performing someone else's. The woman (who doesn't speak English) looks directly at you (who does) and says (in French): "performers who do covers face different problems than musicians who write their own stuff -- they call them 'song writers' in English."  Et alors? What's the point of saying "song writers" in English? Long pause, during which she's silent; she's waiting for something. What? It's highly unlikely that she's asking for confirmation. You respond in an even tone: "On dit 'composers' en anglais" (we say 'composers' in English) then add: "C'est quoi le rapport ?" She can't figure out your angle and remains, momentarily, speechless. Hooray. 

Example Two: You buy a large bar of dark chocolate at the local épicerie. Later at home, you open the package and find speckled, grey, unappetizing chocolate that has obviously undergone some severe temperature change. The next day, you go back to the store to exchange it (not a common practice in France). You explain to the épicier that the chocolate has gone grey and is therefore not desirable to eat. The épicier looks at you in disbelief and asks: C'est quoi le rapport ? His wife has recently used a similar grey bar to make a delicious cake, dark chocolate is for cooking anyway, not for eating." You re-phrase: "I bought it to eat, not to cook with." Him: "but you cook with dark chocolate; you need to buy milk chocolate if you want chocolate to eat." (Mais franchement, j'hallucine ou quoi ?!) You could counter with another "c'est quoi le rapport" but it's a losing battle. You insist simply: "We like to eat dark chocolate. Do have any that's arrived recently, that may not be discolored?" Him: "Je vois pas le rapport..." After another ten minutes of this, you finally head back home with a new bar of dark chocolate.

Moral: if you want to hang out with the French, you'd better be tenacious or very, very zen.