On a big system like the T (several hundred thousand riders on a weekday), you'd expect a certain amount of weirdness. You'd be right. Some examples from 2012:
T police kicked out some well meaning but permitless carolers at Forest Hills ; in one of her first executive decisions, new GM Beverly Scott agreed to let them back in - and joined in :
The T inaugurated bananaphone service  on the Green Line:
The Red Line countered with Banana Rastaman service .
A cat was lost, then found  on the Red Line.
The Orange Line was delayed due to coffee .
An angry man confronted riders at Andrew with a plunger .
Charlie took a ride on a Swan Boat :
The Red Line was delayed by the discovery of a mystery item - which turned out to be one of those gizmos Cambridge meter maids use to write tickets .
A woman whose car wound up on Green Line tracks on Beacon Street blamed her GPS .
Melinda Green provided proof that, yes, all those Sob Story people do collaborate:
Nikki captured the painter at work on the Red Line :
The Fitchburg Line was delayed due to horse .
A man used a box cutter to slice open a lemon  on the Red Line, then ate it.
That woman tried going up the escalator in her motorized wheelchair .
A bus rammed into a trailer  for a Sandra Bullock movie in Dudley Square.
The Riverside Line was delayed due to turtle .
A bank robber without a car took the T instead .
The limber can always get a seat on the Green Line .
The finest hand-crafted subway map in the world made its appearance on the Red Line:
A man rode the Blue Line with an iguana on his shoulder .
An alleged Green Line exhibitionist claimed jostling on the crowded trolley made his shorts fall off .
Some people on the Red Line are just trying to get a head .
Somebody with access to the MBTA Transit Police Twitter account tweeted he was bringing a 12-pack .
Say, we don't get many sax-playing luchadores on the Red Line .
A guy tried riding his bike up the escalator at Forest Hills, wound up spilling his coffee at the top .
- Boston 
- The T