Some things just never fail to cheer me up.

Ms Woo: There's this other social network I've heard about, like Facebook and Twitter...
Girl: Tumblr?
Ms Woo: Yeah, Tumblr, that's it! A lot of people are saying it's really good. Is it really?
Girl: Yeah, it is!
Dude: Ew, who uses Tumblr? Facebook is so much better!
Other Dude: Well, you can't really compare the two, right? I mean, it's like comparing an apple with a... car.
Ms Woo: xD So I'm guessing Facebook would be the car?
Other Dude: Or like... a leaf with a microwave. It just doesn't work.

(introducing biological drawings in Science)
Hazlewood: ... So if you see like a squiggle and you don't know what it is, don't just label it randomly. I'm warning you, I've done this every year and I know exactly what's supposed to be labeled in your drawing, so if you fuck up— (dead silence before realisation hits and he covers his mouth) Oh.
(cue class bursting out into hysterical laughter)