FROGGIT:

"Meow."

Froggit is the first and most common monster type encountered in the ruins at the start of the game, and seems like nothing more than a big frog until you realize that's a face peering out from the shadows under its body. Those eyes even blink! What on Earth is going on with Froggit? Is that the "real" monster, hiding under a fake frog-like body?

ICE CAP:

"HELLO??? My hat's up here."

Maybe Arktos is to blame, but I've really grown to like ice-themed monsters in recent years, especially when they're ever-so-slightly-creepy snowmen or ice golems. Ice cap is an especially fun one, with its spooky eyes, drill-nose, and fixation on its own elaborate, enormous ice hat. Complimenting its hat is one way to spare it and end the battle, but you can also take its hat, which reverts Ice Cap to nothing but a sentient ice cube. What's with snowmen being powered by their hats!?

GYFTROT:

"Goshdarn teenage googly eyes!"
I never thought I'd find a festive holiday reindeer monster so cool, but Gyftrot's twisted face and cranky personality won me over. Residents of Snowdin village apparently decorate Gyftrot's horns like humans decorate their enslaved evergreen trees, but Gyftrot just wishes it could be left in peace. Un-decorating Gyftrot, and giving it a present of its own, is the key to winning a fight against it peacefully.

JERRY:

"Can YOU give me a ride home?"

Designwise, Jerry looks a whole lot like your typical Japanese "martians," though just a little wonkier and more awkward. Personality-wise, Jerry is an unhygienic, hyper-critical, whiny, selfish, obnoxious nerd that nobody can stand, and that's actually integral to "defeating" him. Jerry will always appear - uninvited, of course - alongside other monsters, complaining all the while until you help the other monsters ditch him, and can finally ditch him yourself. He's even one of the only monsters excluded from the end credits!

TSUNDERPLANE:

"No way! Why would I like YOU."

Tsunderplane, the tsundere plane, was apparently the brainchild of a kickstarter backer, and whoever you are, bless you. Why an airplane with a hat lives in the underground monster realm is impossible to guess, let alone why its entire personality is defined by feigning disinterest in its various crushes, but I'm glad it exists. I'm glad we can defeat a living airplane by flirting with it into embarrassment.

MOLDESSA:

"You adjust Moldessa's face."

Appearing only in hard mode, Moldessa is my true love a marvelously unique take on a slime-like enemy, a big glob of moldy ooze roughly in the shape of a humanoid bust with pigtail-ears. Moldessa's crude, eerie face is a thing of beauty as-is, but she's apparently intent on having it "fixed," and you can actually rearrange it for her until she's satisfied. AWWW.

SHYREN:

Shyren is a unique character and exceptionally adorable battle, initially facing away from the player until you start humming to her sireny song. Keep at it, and she'll not only open up and face us, but the battle text assures us that Shyren and the player take some to go on tour as wildly popular musical icons before parting ways.

What's especially interesting about Shyren is that her mermaid-like appearance is just a ruse. Her "head" is her true body, just a darling little hairy anglerfish, while the "body" is a seperate, slug-like creature, the "arm" in her sprite actually a part of its huge, sucker-like lips!

ENDOGENY:

"You pet the Amalgamate. It starts to generate a Stage I Happiness Froth."

Endogeny is the first of several disturbing "amalgamates" from a secret, optional laboratory near the end of the game. I won't spoil who created them or why, but rest assured, even these oozing, twitching abominations respond positively to kindness and can be spared, with heartwarming post-game results.

Endogeny is a fusion of five different dogs, and if you didn't see it already, their outlines are formed by the space between its many legs. Pet and play with Endogeny enough, and ghostly, disembodied little eyes and mouths will even begin to appear in those negative dog-spaces. That is weird.

MEMORYHEAD:

"It's a real get together."

Another amalgamate, several of these creatures appear oozing out of a filthy old sink, each resembling multiple heads and faces melted together in a seething globule with a spinal column tail. Impervious to all other attacks or actions, the only way to defeat the memoryheads is, for whatever reason, to call them on your phone.

LEMON BREAD:

"Do you think I'm pretty?"

You'll notice some similarity between Lemon Bread and Shyren, though she also incorporates aspects of two other monsters. The slug-like symbiote body is even sluggier and gooier here, while the head just a ring of "teeth" formed from pieces of the slime enemy, Moldbygg. The floating teeth she attacks with, coupled with her name, feel like they might quite possibly be a reference to the notoriously weak but lovable Melon Bread from Gunstar Heroes.

UNNAMED AMALGAMATE:

"It's so cold."

This amalgamate is similar in structure to another enemy in the game, but with vegetoids instead of eyes, a humanoid figure in the middle of its face and a half-melted body, it's barely recognizable at all, and supposedly contains over a dozen other monsters melded together. It's never given an official name, but we do find out who this amalgamate really is if we've paid enough attention to the right NPC's.

,:

"This relentless future finally looks brighter and brighter."

Yes, this monster's name is just a comma, though it's also been less formally called "reaper bird." Its head is actually an earlier, eye-demon enemy turned on its side, while the body is comprised of parts from two other monsters, the final froggit and the whimsalot. "," speaks with the dialog of all three, but overlaid atop one another into nearly unreadable gibberish. Unlike most of the amalgamates, it never appears again after its defeat - not even in the game's credits - and we never learn anything more of its backstory, though it boasts possibly the most intriguing attack animations in the game...

EVERYMAN:

This enigmatic entity never appears as an actual monster itself, but appears during the "," battle as the amalgamates method of attack. Everyman will first appear just standing there, doing nothing, as a swarm of butterflies devour its face. Neither Everyman nor the insects make any move against you, and you can simply wait out the whole sequence without even moving. Unfortunately, Everyman will start staggering around the battle screen for the next attack, as butterflies scatter in all directions. Following this, Everyman's next move is to regenerate his head and throw it at the player, again and again until the turn is over.

Everyman's cycle of butterfly-attack and regeneration will repeat itself under "," is defeated, and while it's a pretty close competition, I think this might very well be the most unsettling thing in the game. What is Everyman? What is its relationship with ",?" Why the butterflies?

There are deeper mysterious in Undertale, and dramatically more frightening creatures, but it's Everyman that I keep thinking back to.