My DS3 has always enjoyed copying people since he was a baby. I remember him when he was about 1 copying the noise a baby was making at the other side of co op with a huge grin on his face.
If we take him to the park he’ll run and play with the kids but he’ll copy what they say. So if they say “shall we play on the slide?” He’ll repeat that sentence in exactly the same way. If one of them runs up to their mummy and then jumps and then says eg ”my brother fell off the slide, he’ll copy their movement of running, jumping and repeat the same sentence.
We went to a bouncy castle recently and a kid was jumping and then lying down. DS copied this exactly behaviour lying next to the other child until the other child stood up and did something else. DS then copied this.
He’s fine in everything else, talks well, very social, it’s just this copying behaviour which I find very strange.