I've got a really good friend who has a DD exactly same age as my DS (nearly 5). We went round to her house and while they were playing together, her daughter was constantly running up to me and telling tales on my son.
Example 'he is sticking his tongue out at me', 'he is telling me he doesn't want to play with me' etc.
Yes he is my PFB, but I do know that he can be naughty/cheeky/rude sometimes and I tell him off when I think I need to, so I imagine that, yes, he was doing those things. But to be honest I was getting annoyed after the 50th time she came over to tell me what he was doing.
My friend just looked at me each time it happened and waited for me to respond to it. Most of the time I didn't think that the offence was serious enough to warrant me saying anything to DS so I just said something like 'oh dear' or 'never mind' and continued with my conversation with other adults.
I think what bugged me the most is that, knowing the two children, they prob both said or did an equal amount of nasty things to each other as children do but my DS didn't come and 'tell' once - he just got on with it and sorted it out between them in contrast to my friend's DD who came over about 50 times! So it looked like my child was the terribly behaved one and she was the angel.
Friend did acknowledge that her DD was telling tales a lot but she said there was nothing she could do about it as the school she goes to (DD also in reception year but diff school) had taught the children to tell the teacher if another child does something naughty.
It is not a big deal and won't affect our good friendship but I did wonder if I could have handled it better and stuck up for my DS a bit more as he was being painted (unfairly in my opinion) as this really naughty person.