Here are a couple of ways of making up funny verses. The limerick is, of course, well known. It is five lines long, and usually has something to do with a place. For example:
There was a young man of Nepal
Try composing your own limericks. Get one passenger to think of a place-name, and then allot five minutes for writing. When time is up, the various limericks are read out, and the best and funniest is chosen as winner.
A clerihew is even easier to write. For a start, it is only four lines long, and is made simply of two rhyming couplets. For another thing, the lines don't need to scan (i.e. they don't all have to be the same length). On top of this, the first line is simply someone's name. The poems can be as silly as you like, but they must have something to do with the person mentioned. Here are two examples of clerihews:
Sir Christopher Wren
W. G. Grace
An obvious starting-point for your own clerihews is to use the names of your fellow passengers. Try not to be too rude though!