Butterfree and Venomoth Definitely Got Swapped During Development

I've heard this theory floating around, but I've never seen a full writeup of all the evidence for the switch. Here's that writeup.

I'm fairly sure that the Pokemon Butterfree and Venomoth were swapped at some point in the development of Pokemon Red and Green ^[1] "Green?" For those who don't know, the first Pokemon games that came out in Japan were Red and Green version in 1996. Later the same year, the updated/enhanced Pokemon Blue version came out. When the games were brought to America, they were based on this later version. . Specifically, I'm saying that the appearance of the two Pokemon were switched. The names and stats didn't get switched along with the sprites. I don't know whether the switch was intentional, or if it was an accident, and I definitely can't tell you when it happened, but the evidence is pretty good that it happened.

What a "swap" means

So, if two Pokemon's looks got swapped before development, how could we even know? After all, there's no released media with the theorized "original" evolutions. All we can look at is the games that actually came out. What we're looking for is things that fit better in one evolution than the other. Most of the evolutions in the original 150 Pokemon can be described as "it's bigger now" or "there's three of them now". Even in the ones that change more, they keep certain design motifs and visual styles. Charmander's tail-flame sticks around on Charmeleon and Charizard. The Nidorans keep their horns and large ears. So if there was a swap, then we'd expect Venomoth to share a lot of motifs in common with Caterpie and Metapod, while Butterfree has more of a resemblance to Venonat.

To investigate this, it'll most helpful to look at the oldest appearances we have available: the Pokemon Red and Green sprites. These will be the designs that were created closest to when the swap took place, and so there was the least chance to work around and cover up the swap. Besides, these games are infamous for being rushed and full of mistakes, so if the swap was accidental then it definitely happened close to the release of these games.

What a swap DOESN'T look like

I'll start by going over a different "swap theory" that's been raised for years: Gyarados and Dragonite. The argument more-or-less goes: Magikarp is a fat orange fish that evolves into a blue serpent dragon. Dratini and Dragonair are blue serpents that evolve into a fat orange dragon. Doesn't it make more sense if those are swapped? On its face the idea makes sense, but it falls apart completely when you look at the finer details. Let's take a look at the R/G sprites.

The biggest problem with the dragon swap theory is that, when you look deeper, both families make perfect sense as evolutions. Gyarados carries all sorts of visual motifs and hints of its original Magikarp form. Look at the three-spiked fin on the top of Karp, and then look at the same fin on Gyara. Look at the gaping open mouth, the whiskers, the rounded scales. They're all there in both sprites.

On top of that, there's the design inspiration. Gyarados is based on a Chinese legend of a carp climbing a waterfall with a gate on top. Once he climbs through the gate he transforms into a dragon, just like Magikarp has to "climb" to level 20 to transform into Gyarados. The thing to notice is that this is a Chinese legend, so our carp should evolve into a Chinese style dragon, which Gyarados is. Now, let's look at Dragonite.

There isn't as much to talk about with this family, since there aren't as many motifs in common. Still, Dragonite isn't actually out of place in this family. He carries the round, friendly face of Dragonair and the striped belly of Dratini. In these sprites he also looks a lot slimmer and more serpentine than later versions. For some reason Dragonite gains weight as Pikachu loses it.

In summary, Dragonite and Gyarados are strange evolutions on the surface, but when you look deeper both of them actually make perfect sense. If they were swapped, all those connections and shared motifs would vanish. Sure, Dratini's face wings resemble Gyarados's, and Dragonite's horns look like Magikarp's whiskers, but those are the only things they have in common.

Back to Venomoth and Butterfree, let's check out the evo lines. Caterpie is a biologically-accurate caterpillar with biologically-inaccurate big white eyes. Metapod is a biologically-accurate chrysalis with biologically-inaccurate big white eyes. Butterfree is... a Venonat with wings. Completely biologically inaccurate bug, with four limbs instead of six, no real signs of a carapace or exoskeleton. Oh wait, there is one biologically accurate thing: the red compound eyes. And Venomoth is a biologically-accurate butterfly/moth with biologically-inaccurate big white eyes.

The connection between Venonat and Butterfree is clearest in these original sprites. Same antenna, eyes, mouth, hands, limb count, color. It's hard to write anything convincing about these; I literally don't know what to say if you can't see the similarities.

I can't talk about Caterpie without mentioning that it's real. It exists in real life, and people see photos of it and go "wow that's Caterpie".

This is the Papilio Xuthus, or the Asian Swallowtail Butterfly. Notice how the caterpillar even has the same orange horns as Caterpie. Metapod is pretty plain, but still has some resemblance to the pupa; they share a kinda angular sharp bit near the head. Oh, and doesn't it look like Metapod's head should turn into something else sharp, like Venomoth's horns? Why else would it be pointed like that instead of round? On top of that, Papilio Xuthus is a yellow butterfly. That might seem irrelevant, but some of the oldest art for Venomoth features yellow spots on the back of the wings.

Oh, and one more thing, ^[2] did you wonder what a "swallowtail butterfly" is to start with? Well, a swallow has a long forked tail, with a sort of V shape to it. The swallowtail butterfly has these long slim parts at the end of the lower wings. In the butterfly picture above, you can see one of those little tendrils at the bottom right fo the photo. Now, give Venomoth one more look, and you'll see the exact same swallow tail tendrils.

Bonus Round: The Coverup

When you look at the sprites from Blue, you can see a few clumsy attempts to make the swap less obvious. Metapod curves forward instead of backward, now matching Butterfree's feet-forward curled position rather than Venomoth's arc. Venonat and Venomoth also changed poses, both so that Venonat isn't standing completely identical to Butterfree, and also so Venomoth doesn't look like it lost all its legs.

But Why Does This Matter

It doesn't