This actually happened to me today. It's fantastic.

I swear every word of this is true by whatever measurement you care to require.

BART.

I sat in my seat; window seat.

An older - well, small - person, a woman(?), sat down, facing away talking to someone. Totally ignoring me; I was part of the scenery. A little close! I might as well have been a stuffed pillow. That's cool. I play Bejewelled.

She turns to face forward. I'm looking at my phone. She kind of nudges me with her shoulder. I turn to look.

NOT an older person. Not a woman - a dude. Something... familiar. Can't place it but I don't want to stare so I look ahead. Kind of feeling a bit crowded. I am very attentive to my phone.

Shoulder nudge. I look over again. Ah! This person has Down Syndrome - as does my oldest sister, Kathryn. Okay, this is familiar territory! So, I look around to see if he is travelling with a group or has another travelling companion.

No companion. No group.

Shoulder nudge. He leans in; "mumblemumblemumble". Looks at me intently. I don't understand a thing he said. We are at the Oakland 12th Street station on the Pittsburg/Bay Point train. HE SEEMS TO BE BY HIMSELF. 

OKAY. I DON'T WANT TO PLAY ANYMORE.

I look back; smile. Nod my head. Smile - chuckle a little.

"HAHAHAHAHAHAHAHAHAHAHA!!!!!!!!!!" Big smile. Turns to his left, away from me. Talks to... someone? No one? I can't tell.

OMG. What if he is alone? I can't just... leave him here. How am I going to get him out of the train to the police[*] - what if there IS someone with him and I am accused of kidnapping this guy? HELP. I WANT AN ADULT.

Shoulder nudge. Head bump. HE BUMPED ME WITH HIS HEAD LIKE MY CAT. "Mumblemumblemumble." Stare. I look back, bemused, chuckle. "HAHAHAHAHAHAHAHAHAHAHA!!!!" He turns away.

Repeat.

Repeat. etc. Thankfully my companion was entertaining without being a problem. He was just having a good time, it seemed.

We are now at Orinda station. The train has emptied quite a bit and my boon companion does something else that is... familiar.

When I lived at home Kathryn had a stance that was not sitting but not quite standing - it was her saying "I'm ready to go, lead me" to... whatever it was that Kathryn wanted to get to. The car. The bathroom. Whatever.

My companion now was showing that exact same stance. It was almost spooky. OMG. HE IS CONSIDERING LEAVING THE TRAIN. WHAT DO I DO. THIS WAS NOT IN THE MANUAL.

Ah! He does have a companion - looks like a sister. She sat him next to me as there was no other option; she was sitting on the other side of the aisle and behind. She had secured a window seat for her brother and then she, herself, sat in the aisle to block him getting out.

I smiled and made it plain that everything was fine; she seemed to want to drop things ASAP and nodded, then looked away to her phone.

I got off at Concord; they were still in their seat.

I hope my next BART ride is somewhat more boring.