Q:

What is the difference between 做番 vs. 做返?

A friend (Mainland Chinese, living in Hong Kong) recently posted the following sentence on Facebook:

聖誕節買禮物?做番中國人啦!

As I had never seen the "做番" construction before, I asked if perhaps she had mistyped the phrase, and had wanted to use "做返" instead, seeing as the pinyin would be the same for both. 
She responded that, in this case, both were OK. 
Is her assessment accurate? Why would one use "做番" instead of "做返"? Is there a subtle difference in meaning?

A:

Both 做番 and 做返 are used to represent the Cantonese expression, jouh fāan.
There is a reason why some people choose to write 番 and others write 返.  Etymologically speaking, 返 is the correct character to use.  However, because the traditional literary pronunciation of 返 is fáan (2nd tone) instead of fāan (1st tone), some people will write 番 instead to make it explicitly clear that the 1st tone reading is intended (even though the original usage of 番 has nothing to do with 返).
Because written Cantonese is not standardized, both characters are typically seen; so your friend is not wrong when she said that both are okay.
BTW, the reason why 返 came to be pronounced in the 1st tone rather than its traditional 2nd tone is most likely due to changed tones, a phenomenon that affects various words in Cantonese (this phenomenon somewhat analogous to how erhua affects various words in Mandarin).

A:

While officially there is only one Chinese written language, there are many spoken dialects. This written language is referred to as 白话 (báihuà) and is used across China. The spoken languages (i.e. dialects) can differ significantly from 白话 - both in vocabulary and in grammar. Thus, spoken Cantonese differs substantially from 白话. It is key here to realize that the spoken Cantonese language and the official written language (白话) do not correspond to each other! 
There is a trend in certain dialects to actually write down the language as it is spoken, which means the syntax, vocabulary and characters can differ from those found in 白话. For example, the site Canton 168 – 廣東一路發 gives the following example: 
Mandarin: 我們明天可以去香港    Cantonese: 我聼日可以去香港
This trend for using written Cantonese is most pronounced in Hong Kong. Because this is not an official written language, people themselves must agree on what characters to use in written Cantonese. Over time, certain characters become more popular than others and thus become the de facto character to be used in a specific word. For 做番 and 做返, 番 and 返 are two competing characters, with some people preferring one and some the other. 
做番 and 做返 thus represent written Cantonese, not 白话, and are two different ways to write the same word! As Zannjaminderson pointed out in a comment above, in 白话 the term would be rendered as 做回. 

A:

It's a Cantonese construct, which is why either one is fine - there is no official way to write this in Cantonese.
The equivalent in Mandarin is 做回.

