Rhymes

There is a lesson in class about rhymes. The teacher asked kids if anyone knows a rhyme already? Little Johnny lift his hand up and responded: "I know it!" "Ok, Johnny, tell us your rhyme" the teacher said.
"There's a dog in the grass and you can see his ass" Johnny said proudly almost singing, but the teacher angry responded: "You cannot say that word in the class!! If you want to say that properly without saying the ugly word, you can say: There's a dog in the grass and you can see his a...! and we will all know what you meant, without you saying the actual word, understand!"
"Ok"
"So does anyone else knows a rhyme?" teacher asked. Nobody responded and teacher wanted to start the lesson, when Johnny said again: "I have another one!"
"Ok, Johnny, tell us the rhyme, but remember what I told you!"
Johnny said "Yes, I remember!" and started with the rhyme
"My friend is really tall but his dick is s...."