There was a kid like this at school who we thought had a learning disability or some variety of Brain Problems. It was especially concerning because he was at frikken level 0.5 for reading and the school year was two-thirds in (for reference, in our system grade ones are supposed to start at roughly 4-5 and end the year at 18-20 and "chapter books", which some grade one kids do get to, are basically anything past lvl 24).
There were other kids who absolutely had learning disabilities who did also say random-ass shit sometimes (my personal favourite so far is "Hey Mister Matthew? Did you know that New York is coming to Toronto?" which was definitely NOT a reference to any sports matchup), but this poor kid was seemingly in another dimension.
It turned out he just needed to take ESL classes. Within three weeks he was at level 12 and pretty much everything he said was comprehensible.
I'd seen kids struggle with language issues before, but that was just such a weird manifestation, because his English sounded fine, it's just the content which was all haywire.