Is that vegetable oil?

Very late to the party here, but the joke is that Sanpoll is extremely dangerous if mixed with caustic cleaners such as bleach - it gives off toxic levels of hydrogen sulfide and chlorine gas.
The warning label - "Danger: Do Not Mix" has become something of a meme online, used in response to particularly chaotic mashup videos: https://dic.nicovideo.jp/t/a/%E6%B7%B7%E3%81%9C%E3%82%8B%E3%81%AA%E5%8D%B1%E9%99%BA