Zhè shìr méi tā shénme fèn, tā piān yào shēntuǐ jìnlai.
This is none of his business, but he insists on muscling in.
Tips
usage
Three layers: literal stretch (most common), figurative 'sticking your leg in where it doesn't belong' to grab a piece of something, and a euphemism for dying ('stretched his legs out' = laid out, dead). Context disambiguates.