Donate your sister
From China Digital Space
捐你妹 (juān nǐ mèi): donate your sister
After record rains hit Beijing in June 2012, the Red Cross requested donations. Netizens, skeptical of the Red Cross after a series of scandals, responding by posting en masse, “donate your sister.” In Chinese, "verb" + "your sister" is a curse word.
The phrase "donate your sister" was censored for a time on Weibo.
A paper that reads "your sister" is being dropped into a donation box.
See here for a discussion of the flood and citizen reactions to the government response.