"favourite fairytale" is featured in a few of the correct translations. So, if your sentence was rejected it wasn't due to that phrase. There was something else that caused the rejection. Just giving us 2 words doesn't really help.
You should have made a REPORT.
TIPS TO MAKE LEARNING EASIER + HOW TO REPORT A PROBLEM https://forum.duolingo.com/comment/22424028
https://forum.duolingo.com/topic/936 If you have any questions just ask.
Please don't comment about rejected sentence unless you have first made a report.
Hi! I understand that we should make a report when we are certain that our version is correct and should have been accepted. But what about cases where we are not sure whether our version was correct or not? Should we still make a report in those cases, or first discuss the answer?