Seeking Games with LIs that have mentally challenged/special needs (or have mental retardation)

[Maria2clean]

As the title suggests I'm looking for games that have mentally challenged LIs. And not LIs that are written poorly or act in a stupid way even though they're shown to be capable of normal thinking. Nor dumb LIs like Lily from Where the heart is.

I mean, just mentally challenged/mentally retarded. Think like having the body of a 20 year old but mentally 5 year old.

Thanks!