Become Penpals with an Alien (Pigpen Cipher Activity)

Graphic of an alien saying "Greetings Earling!" in a Pigpen cipher

I’ve been trying to find new and engaging activities for my two little boys. Lately I’ve been doing a huge deep dive into all things secret code/cipher related. Activities that get their imagination going, suspend reality for a bit, and are engaging for both them and me. 

I’ve been racking my brain on how to best incorporate some of my new cipher and secret code findings. Right now I’m sitting in my comfy living room chair watching my two boys write pen pal letters to their grandparents. 

There’s something exciting and special about how they can put a little sticker on the top of an envelope and it magically travels to another part of the country. What makes them even more excited is that in about a week, they’re going to get a letter back. 

And then my oldest gives me some great inspiration. He loves using the pigpen cipher from the moment I showed him how it works. And then he tells me what he loves about the pigpen cipher is that it looks like an alien language. 

Cue light bulb, I just found my idea. What if they were to get a letter from space? What if it was all written in this weird-looking language (that would take some time for them to encode and decode)? I think I’m onto something. 

But first, I need to come up with an alien messaging system.

If you want to learn more about the Pigpen Cipher, check out The Pigpen Cipher (What it Is and How to Teach Your Kids).

How to Build and Alien Messaging System

So here’s the premise. I took a PVC tube with a cap on one end and a threaded plug on the other (I’ll show you exactly how I did it in a bit). The whole thing will be painted in a space ship gray. Then I paint each of my kids’ names on it using the pigpen cipher. 

Finished Alien messaging system
Finished Alien Messaging System

As long as my kids have been introduced to the cipher they should have no problem identifying the text and solving the cipher quickly. 

After typing up my message I’ll put it into the tube. Sometime after the kids go to bed the messaging tube will “crash land” in the middle of the backyard. 

After the kiddos decode and read the message, they can then write back by leaving a message in the tube and putting it back in the crash-landing site. There it will be “beamed back to the ship,” thus beginning our ongoing alien correspondence. 

So let’s move on to the details. 


Remember that this is not exact science here. We’re essentially creating a prop. Feel free to follow what I did exactly (I’ve included links to Lowe’s and Home Depot) or deviate completely and use whatever you have lying around. 

  • 1-1/2 in x 1 ft PVC pipe (They usually come in segments longer than 1 ft. Usually the shortest is 2 ft.)
1-1/2 in x 1 ft PVC pipe
  • 1-1/2 in x 1-1/2 in Hub x Hub Schedule 40 Cap 
1-1/2 in x 1-1/2 in Hub x Hub Schedule 40 Cap 
  • 1-1/2 in x 1-1/2 in Female x Hub Schedule 40 Adapter
1-1/2 in x 1-1/2 in Female x Hub Schedule 40 Adapter
  • 1-1/2-in x 1-1/2-in Male Schedule 40 Plug 
1-1/2-in x 1-1/2-in Male Schedule 40 Plug 
  • Gray/silver spray paint – flat or glossy depending on the look you want. I went with flat (optional)


Cut your PVC pipe to about a foot long (you can either use a hand saw or a miter saw for this). If you have any rough edges, clean the end with some rough sandpaper (specific grit isn’t super important. None of this will be seen so anywhere from 80-300 grit should do the job.).

Put the cap on one end of the pipe, the female threaded hub on the other end, and screw in the cleanout plug into the threaded end.

Glued Alien Messaging System
Glued Alien Messaging System

For those of you with any experience with plumbing, you absolutely can use the purple primer and PVC cement, but I don’t think it’s necessary. We’re not actually using this for plumbing. 

In fact, you shouldn’t need to glue anything together (fits should be snug enough), but you can always use some CA (crazy glue/super glue) or polyurethane glue (gorilla glue) if you need to glue any of the parts together. 


To paint and decorate the whole thing, you can get super elaborate, or super simple. While I used to nerd out building model airplanes as a kid, I’m going to keep this paint job simple (FYI, I’m not artistically minded).

Paint the whole “device” with two coats of gray (or silver. Whichever you choose.) spray paint. Remember that it’s better to do multiple lighter coats than fewer heavy coats. Even if the can says “no runs” on the paint can (like my paint can did), it can still have runs (which mine did).

Whatever color you decide to paint it, remember, this is supposed to be fun for you too. You just don’t want it to look like a PVC pipe.

Finally, paint your kid’s name on the outside using the pigpen cipher. You can do this with a permanent marker or mask it out with some blue tape and paint a light coat of black paint. (It’s okay if it’s not perfect. Mine is far from it. It had a long trip in space, remember?)

Masked Alien Messaging System
Masked Alien Messaging System
Painted Messaging System
Painted Messaging System

How to Encode and Decode Your Message Using a Pigpen Cipher

And it’s at this point that I should actually take a minute to explain what a pigpen cipher is. Basically, a pigpen cipher is a substitution cipher in which you replace the letters of the original message with geometric symbols.

You can find a much more thorough explanation in my post The Pigpen Cipher (What it Is and How to Teach Your Kids).

You begin creating the cipher by drawing two tic-tac-toe and X patterns. Each second tic-tac-toe and X pattern have dots. Then write the alphabet inside each section of the grid.

In order to code your message, replace each letter of your original message with the fragment of the grid. 

Pigpen Cipher Chart
Pigpen Cipher Chart

Using the chart, we can encode the following message:

Graphic Showing "Greetings from Earth" and how it translates to the Pigpen Cipher.

Luckily for you, you can download a font for a pigpen cipher (there are a couple places you can download it for free. I used This is not an affiliate link.). Now you can type your message normally, and then just change the font. Super simple!

If you want to teach your kid more ciphers, check out 6 Secret Codes and Ciphers to Teach Young Kids.

Sending Your First Alien Pigpen Penpal Letter

Now onto the first letter. 

You want to make sure you set the right tone here. Make sure your language isn’t ever threatening, that you’re interested in learning more about Earth, and that you’re looking for a friend. You don’t need to give your kid nightmares about a potential alien invasion. I like my sleep a little too much to go there. 

Begin by introducing yourself and that you’re on a peaceful mission to learn about life on other planets. Ask about what school is like, what food is like, what animals are like, what Disney World is all about, whatever. 

If you want to go the extra mile, learn how to How to Weather Paper to Make it Look Old (The Ultimate Guide).

You can even make this more educational and have them research what a dolphin is and have them explain the different species. If your child is into music, have them explain what a metronome is and what are different kinds. Or how to Make Your Own Gummy Bears with Kool-Aid Mix. Use this as an opportunity to teach your kids new things and then explain them to their new alien friend.

When you get to the end of your message, be sure to include directions on how to leave the special message device back in the yard so you can collect it in the night. Be sure to also let them know you will message them again in a week (or whatever amount of time you will take), just to help establish expectations (and not get the nagging annoying constant questions. You know what I’m talking about.). 

If you’re still a little stumped about what to write about, here’s my first letter (first in a normal font, and then encoded using a pigpen cipher). Feel free to download it and use this same message (don’t worry, I’m not collecting information. This is genuinely free.). 

Now, you might be thinking, where do I go next with this whole alien pen pal thing? Am I going to have to have a difficult conversation like explaining about Santa Claus? 

Alien pen pals is a great set up for what’s about to be my epic alien treasure hunt. Stay tuned for a future article!

You might also like these Treasure Hunt activities:

Gregory Grabowski

Greg Grabowski is the principal creator of, a website for dads by dads. Inspired by his two boys Ben and Sam and his wife Dianna, Greg loves to make things, learn things, and loves doing fun stuff with his family.

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