If I'm thinking anything at all, it goes something like this:

• “I wonder where all these people are going”
• “I wonder if any of these people are truly happy with their lives”
• “I wonder where [he/she] got [his/her] [shirt/jeans/coat/scarf, etc] from”
• “I really hope that weirdo gets off at the next stop”
• “Why is [he/she] staring at me?”
• “I wonder what the driver’s thinking”
• “I hope I can squeeze through all these people when I’m getting off the bus before the driver closes his doors and drives off”
• “I wonder what that baby will grow up to be”
• “I seriously need to learn to drive...”
• “I wonder what that unfriendly looking group of [teenagers/drunks/men/fat people, etc] will do or say to me when I squeeze past them on my way off the bus. Hopefully nothing…”
• “I wonder if one day I’ll get to know [him/her]”
• “Please, please, please don’t let anyone drunk, smelly, insane or scary sit next to me!”
• “I wonder what [his/her] hopes are for the future”
• “I wonder what [his/her] name is and whether [he/she] is named after someone”
• “I wonder whether any of these people have had an effect on my life in the past”
• “I wonder which of us is the smartest”
• “I what [he/she] likes about [him/her]”
• “I wonder how [he/she] ended up right here on this bus with me”
• “I wonder what [he/she] is worrying about right now”
• “I wonder whether the driver is feeling particularly irritated with his passengers today and plans to drive us all into a brick wall at a very high speed… I hope not.”
• “I hope I don’t trip over anything on my way off the bus”
• “I hope nobody on here is planning something terrible…”
• “Why do they insist on playing songs out loud on their mobiles when there are people on here (like me!) who can’t stand their dreadful music???”
• “I wonder how they met”
• “I wonder what people are thinking about me right now…”