Are Catchphrases only made by a certain group in a certain area? Do people live in Southern America have different catchphrases with those live in Northern America? May I count dunno and wazz up as catchphrases?
A catchphrase is usually created when a line said/written by someone is used very commonly by a group in their everyday conversations. Catchphrases are phrases that catch on from one group of people to another. They are found in most languages and not just in English.
So a question asked by the Joker in The Dark Knight movie, "Why so serious?", might not have originally intended to be a catchphrase although you might have noticed people around you use it during conversations in light humour.
"Dunno" and "Wazz up" on the other hand are not catchphrases. They are a part of the English slang word group and are used informally in different places.