Hi, Y.!
Ok, first let me say I've been through this with 4 of 'em, and I even remember trying it out myself at age 4. What my own mom did strongly influenced my strategies when I grew up and popped out all these kids -- and it worked. Really simple.
-Acknowledge: "Listen, I know you've seen other kids try this out and it seems interesting. But you need to know: I don't hear that kind of voice. I hear your normal voice, like this:" and then I show them, respectfully, the voice I want to hear vs the whiney, annoying voice they're trying out.
- Develop a 'deaf' ear: No matter what they say to me, it HAS to be in their normal voice. If they say, "Mom, my arm fell off and it's blocking the stairs," it STILL has to be in a normal voice. Period. If they whine, I say, "I'm sorry? I couldn't hear that voice..." over and over and over... till they remember what we discussed -- and realize I won't cave.
- Don't give up: Usually they conform quick when presented with resolve and a deaf ear.
- Give a hint: Gently, 'confidentially' remind them that they need to use their big kid voice, kind of give them a hint before you pretend to be deaf because after a night's sleep they actually do forget briefly.
- Occasionally they'll go for a marathon duel --to see if you'll cave after 25 whines... plus tears... plus a mysteriously lame leg and a certainty they may die... but by whine 26 they'll decide they want your attention more than they want to whine.
- NOTE: I've noticed that, without fail, real emergencies NEVER, (and I mean broken-collar-bone, midnight-asthma-attack) NEVER get presented with a whine. There's a whole different sound to a child in real distress. The primal senses get it straight away.
-Bullying: I define this as any sort of strong-arm tactic -- including psychological strong-arming by tattling every 5 seconds. No way around it, I have to sit down and talk it out. Logically. Get down to brass tacks and find out not only who knocked the blocks over, but who frustrated the Knocker so badly that she felt compelled to block-knock! Pretty soon the certainty of equal and just consequences eclipses the tattling compulsion. Heck, if you're gonna get nailed for egging someone on, it's not worth tattling when they retaliate.
- BUT there are some things that I DO want tattled on, like unprovoked violence, drawing on the car, seeing if it's true that a lizard loses its tail when terrified... trial and error teach kids to define and use their moral compasses. It's worth the time invested to help them do that.
I have to run through these routines, at some level, every few months -- because every few months they honestly think I'll forget. It takes about 3 days of 'zero-tolerance' before they stop challenging the 'system' and just get back to being happy, normal kids. Don't be alarmed when they keep refreshing the challenge -- it's a sign they're not dull-witted. Just know your strategy and stand your ground. And above all, praise, praise, praise even the little things they do right. Seriously. It makes ALL the difference.
Good luck! :-)