When I was not long out of school I worked as a copy-editor at a newspaper, under an editor who had an outright phobia for passive voice. Unfortunately for him, us brats who went to school in the 70's and 80's didn't get taught much formal grammar, so he taught us a trick - I've since seen it in lots of places, so I guess it wasn't just his: If you can replace everything after the verb with "by (someone)" and it still scans grammatically it's passive. I forget now what his version of the "someone" was, probably "the queen", but for years now I've used "by zombies" as mine. Because that makes me laugh.
Now it's not a 100% certain trick, it certainly doesn't catch all possibilities, but it's a handy tool. So when 14 year old daughter whined about an assignment from her English homework, I taught it to her. And apparently she taught it to the rest of her class.
So the point of this story: I just got a hysterical phone call from daughter's English teacher, who could hardly speak for laughing. Apparently the entire class turned in their homework with half of every sentence replaced with "by zombies", except for a handful (including daughter, natch) who got extra credit for using "by zombie ninja sharks".
Luckily teacher considered herself well and truly punked and thought it was hilarious.
So nice to know, even at the dreaded age of 14, daughter is minding her mamma :)