I like to make my classes roll their eyes, so today I told a joke I'd just read that had a good effect:
What's the difference between boogers and brussel sprouts? ... Kids will eat boogers.
Or another of my favorites ... whenever we're doing a problem involving x and y, and I prompt them for an answer, and the answer happens to be y ..... when they respond, "y" to my question, I reply, "because I asked you!".
Or when they're finished with whatever they're practicing, and someone calls out, "I'm done" .... I call back, "Stop it. You're not dumb" .... and then they say, "no, I'm finished" .... to which I HAVE to say, "oh, I thought you were American."
Ar ar ar. A wee bit of humor to get through the stressful times.