My grandson is 11, autistic/GDD. He lives 200 miles away with his mum. His dad lives with us. Grandson comes to stay with us for a week at a time, four times a year.
You can't have a conversation with him, so trying to work out what or who he's talking about is very difficult. He will just parrot back - e.g. if you say "what do you want to eat", he will just say the same thing back to you. Very occasionally, he will answer, but if you then ask him something else, he'll just repeat that back to you, and will either forget, or just not want to respond to the first question again.
However, for the last few times he's been to stay, if he goes to leave the lounge and someone says, for example "where are you off to"? he will say "I'm going to play with Gilbert".
He watches CBeebies obsessively, and is addicted to his tablet, so it could be something from there that he's heard. His mum has no idea what it is he's talking about.
It's nothing in the grand scheme of things, but we'd love to know what/who he's talking about.