Innocuous strings which may be blocked by profanity filters (https://en.wikipedia.org/wiki/Scunthorpe_problem)
("Country" is not obscene, but Shakespeare makes "country matters" into an obscene reference in Hamlet. There are a lot of innuendoes in the classics)
Some of the best teaching of Shakespeare I've seen used the actual lines mixed with a little extemporaneity to better get the intent across. "Nay, gentle Romeo, we must have you dance. Come on, stop being so emo! There are like a million other girls out there."
[0] https://www.newscientist.com//article/dn2546-email-security-...
Wikipedia [2] attributes it to a Yahoo email filter "which automatically replaced Javascript-related strings with alternate versions, to prevent the possibility of cross-site scripting in HTML email".
[1] https://github.com/minimaxir/big-list-of-naughty-strings/com...