People that can wiggle their ears, how???

You are really moving your scalp by pulling various muscles in jaw, forehead, back of neck, eyebrows, etc, and your ears go long for the ride.

Put on glasses
Lean forward until glasses hang from your ears
Get tense/angry, notice glasses move toward your face
Relax, notice glasses move away from your face
Repeat 3-4 until you isolate the muscle

Ah I know those muscles to pull your glasses back. Don't notice the ears moving but I'll practice.
- Yep, it's the same muscle. If you've noticed your glasses moving, then you've got it and you just need to practice.
Hah, that's how I learned to do it as well.

Genetic difference. Just like people who can raise one eyebrow. Not all of us have the same muscle control. Likely a leftover from days where we could point our ears towards a sound like small-eared dogs can.

Wait until y'all hear about ear rumbling and eye wiggling...
Anybody can learn to use these muscles. It doesn't just come naturally.
- Some people say maybe. Some say maybe not.
  
  https://www.livescience.com/33809-wiggle-ears.html
  
  https://www.nytimes.com/2017/01/16/science/wiggle-ears.html
  
  “Some people can reportedly improve their ear wiggling by concentration and practice, but they have to have the ability to begin with.”
Just like people who can raise one eyebrow.

https://en.wikipedia.org/wiki/Tongue_rolling

Tongue rolling is the ability to roll the lateral edges of the tongue upwards into a tube. The tongue's intrinsic muscles allow some people to form their tongues into specific shapes. Rolling the tongue into a tube shape is often described as a dominant trait with simple Mendelian inheritance, and it is commonly referenced in introductory and genetic biology courses, although there is some disagreement.[1]

Everyone can do it if they want. I learned how to do it in my teens. It took about a week of obsessively trying until I finally honed it. I even can move the scalp back and forwards due to that same 'training'.

This is how I learned to wiggle my eyebrows.

Look at a dog or similar and think what muscles you would use to move your ears. Try to "listen" behind you.

I like this answer best because it is the most creative.
- It is the best way I can describe for how I learned how.

When I was a kid I just tried flexing any muscle in my face, and if some made my ears move (even a little, or connected to other things), I'd keep trying to do that but also trying to isolate it to just my ears. After enough of that I was able to move them and switched to trying to control one at a time. Now I can do both independently pretty easily

Jaw muscles. They extend up past the ear and over the head.

So you're flexing your jaw muscles?
- Yes. But not the "main" jaw muscle that gives up/down biting force. It's the ones that let you move your jaw side-to-side and forward/back. Especially the forward/back ones.
Not exactly wiggling the ears, but the stuff around it.

The muscles that flex for me are the ones in the back of my head. If you place your hand on the back of your head directly between your ears (so just about where your skull begins to curve in and your neck muscles begin) it's the ones just on either side of the center line that do the flexing and pull my ears back. Try imagining scrunching up the back of your head.

I don't even know how to describe it... It's like how would you describe how you can wiggle your butt? I just flex the muscles on the side of my head and it makes my ears twitch 🤷🏻‍♂️

To find the muscle that does this go above the ear 2 inches and to the rear 2 inches.

Try to "look surprised" or flex your scalp and move that muscle.

Not only it's fun, it helps me hear better because I'm literally perking up my ears. That's what it really is and maybe if you think along these lines you muscles will respond.

I had a friend who just started being able to do it while dropping acid. Talk about mind expanding drugs.

Because I'm happy and I know it.

Not everyone can do it, because the necessary muscles (auricular muscles) are considered vestigial at this point, meaning not everyone has them or doesn't have large enough ones to wiggle their ears. In other words, evolution is slowly deleting them from our bodies as a species, with some of us being "further along" than others.

I listened to a science podcast recently that said anyone can learn to do it in a few hours. The trick is looking in the mirror and trying various things until you get it, then practising that thing.

But it has to be in front of the mirror.

I think practicing unhinging/wiggling my jaw at a young age helped. I blame the Cheerios commercial XD. Also wiggling my eyebrows feels like it benefitted, picked that one up from my grandpa.