WARNING! 小心！ Some of the articles on this site contain words which may cause offence.
Because of the tones in Cantonese, and the close soundings of a lot of words (which sometimes make it quite easy to accidently swear when learning), there are jokes and slang phrases which take advantage of this. I’ve heard jokes in the past which play on words but unfortunately they are beyond my ability.
I’ve translated these from this source as an example, and a lot seem to be insults. They’re quite easy to understand. I’ll probably not use them, but it shows how easy it is for simple mistakes in a spoken sentence to make the whole theme of the conversation change, or make it incomprehensible. Some of the profanity characters have been substituted by the original author, so check the pronounciation if there is a random word in the middle of a sentence.
diu3 haai5／diu3 laa1 maa4 faa1 haai5←→ diu2 hai1 ／diu2 naa5 maa1 faa3 bei1
“crab fishing” / “blue crab fishing monk” ←→ fuck cunt / fuck your mothers cunt
tiu4 lei5 nung4 mou6 cau3 faa3 hai6←→ diu2 nei5 lou5 mou5 cau3 faa1 bei1
“agricultural duties are stinking / disgusting” ←→ fuck your mothers stinking cunt
haam4 haa1 caan3←→ ham6 gaa1 caan2
“bright shrimp paste” ←→ death to your family (a curse)
ngon6 zau1 zau1 / ngaang6 gaau1 gaau1 ←→ ngong6 gau1 gau1
“shore boat / hard platsic” ←→ idiot (fucking stupid / stupid prick)
dung3 ning4 seoi2←→ dung3 lan2 sei2
“iced lemon water” ←→ cold fucking dead
daai6 ning4 lok6←→ daai6 lan2 wok6
“large lemon cake” ←→ fucking big trouble
do1 gau6 jyu4←→ do1 gau1 jyu4
“many old fish” ←→ fucking useless
siu2 laa3 baa1←→ diu2 naa5 maa1
“little horn” ←→ fuck your mother
hat6 daan6 tau4←→ cat1 lan2 tau4
“nuclear warhead” ←→ dick head
biu1 nei5 jau5 mou5←→ diu2 nei5 lou5 mou5
“do you have a watch?” ←→ fuck your mother
ngo5 siu1 nei5 sou3 bou6←→ ngo5 diu2 nei5 lou5 mou5
“I burn your notebook” ←→ I fuck your mother
tiu4 wai6 hou2 mou5 ？←→ diu2 nei5 lou5 mou5
“is it good to mix position?” ←→ fuck your mother
zou6 mat1 nan2 je5←→ zou6 mat1 lan2 je5
“you play what?” ←→ what the fuck are you doing?