English last year, we had a sub, and my friend just takes out a banana and nonchalantly just eats it as the sub is just quietly doing his work and we're all sitting and doing our work in silence. No biggie, until me and my friends (we're all spread out sitting in different parts of the room) just start throwing the banana peel at each other. Soon more fruits get involved and eventually the whole class is just tossing fruits around and the sub doesn't even loving notice at all.
Also in English last year, because our teacher was the coolest guy to walk the campus and still be a "freshman teacher" (as in he just started this year and we were his first class to teach too), we bought him this gigantic basket of useless stuff from Wal-Mart and wrapped it in Hanukkah paper before Christmas break. Included items were: spaghetti, a du-rag (sp? I'm not black), one shoe sole (he was a ginger), some fruits, my little pony dolls and a stuffload of other unnecessary things.
We also pretty much spent all of English class last year on our laptops, using Skype to communicate with each other and laugh our asses off at anything, including pictures we'd send each other. inb4 "omg slacker", we each had like 90+ averages.
Basically English II accounted for like a good 90% of the funny in-class stuff. The last great one I can think of off the top of my head was when we all had to write our own poems, and volunteers/really good poems were selected to actually recite their poems in front of the entire English II lecture hall (every student taking English II basically, ~200 at least). I can't remember my friend's poem at all, but when you looked at the first letter of every line, including the spaces between stanzas, it spelled out "PREPARE YOUR star fish".