Summary:

In probably the second-best part of one of the greatest Undertale fanfics of all time (Alphys' Bad School Day), Alphys and company reach the final portion of their very first day of junior high school in Hotland; why, Gaster's biology class, of course!

However, just like everything else that ends up happening in this story, the class' subject matter of the day is nowhere near what you would expect from any normal school; in fact, the students' assignment for the day is none other than to strap on a set of nanosuits, shrink themselves down to practically microscopic size and venture inside Toriel's body so that they can explore her beautifully vast and complex system of internal organs, and perhaps even theoretically learn a thing or two about how said organs work in the process!

Of course, however, the students' actual intentions during the assignment are anything but educational; in fact, as it turns out, Gaster's plan the whole time was actually to have Alphys and her friends sneak inside Toriel's brain and take control over her body to make her have the sexual intercourse of her life with her husband Asgore in the janitor's closet!

Do I really need to explain how fucked-up this is?
Categories: Giantess, Teenager (13-19), Adventure, Breasts, BBW, Body Exploration, Middle Age (50+), Butt, Couples, Entrapment, Fantasy, Feet, Furry, Futanari, Humiliation, Insertion, Instant Size Change, Lesbians, Maternal, Mouth Play, Nose, Odor, Unaware, Vore, Watersports
Characters: None
Growth: None
Shrink: Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/f, F/m
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 6511 Read Count: 12341

Summary: Immediately following the events of the classic Rocko's Modern Life episode "The Big Question/Answer", when Filburt becomes so obnoxiously, insufferably egotistical and self-absorbed about his new ridiculously beautiful wife (Paula Hutchison) and his absolutely INSANE amount of inheritance money that Rocko and Heffer simply cannot tolerate it any more, they decide to finally get back at him and give him what's coming to him.

How, you may ask? Why, by going inside Hutchison's brain and mind-controlling her into downright BRUTALLY sexually torturing him, then distributing the resulting video recording to the general PUBLIC, of course! Of course, the REAL big question here is this: WILL Filburt ever actually learn anything from this? Tune in RIGHT NOW while you still can to find out!
Categories: Watersports, Giantess, Young Adult 20-29, Adventure, Breasts, BBW, Body Exploration, Butt, Couples, Crush, Destruction, Entrapment, Fantasy, Feet, Footwear, Furry, Futanari, Gentle, Humiliation, Instant Size Change, Nose, Odor, Scat, Slave, Sci-Fi, Violent, Vore
Characters: None
Growth: None
Shrink: Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/m
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 6 Table of Contents
Completed: Yes Word count: 17753 Read Count: 19688

Summary:

In quite possibly THE most fucked-up Undertale fanfic of all time (and probably the saddest, to be perfectly honest with you), Flowey goes inside Alphys' head and takes control over her brain, seeking revenge for what Alphys did to him and his mother back in the Motherly Fuckery and Incestual Apocalypse days. How, you may ask?

Why, only by making her actively, knowingly destroy literally everything she loves and holds dearly and mercilessly torturing her to horrifyingly bloody, violent and gruesome DEATH, of course!

Categories: Giantess, Teenager (13-19), Adventure, Young Adult 20-29, Breasts, Body Exploration, Middle Age (50+), Butt, Couples, Crush, Destruction, Entrapment, Fantasy, Feet, Furry, Futanari, Growing Woman, Humiliation, Incest, Insertion, Instant Size Change, Lesbians, Maternal, Mouth Play, Nose, Scat, Slave, Violent, Vore, Watersports
Characters: None
Growth: Giant (31 ft. to 50 ft.)
Shrink: Lilliputian (6 in. to 3 in.)
Size Roles: F/m
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 2 Table of Contents
Completed: Yes Word count: 14766 Read Count: 11295

Summary: In what can only be described as the much more erotically-focused Parappa The Rapper equivalent to the infamous Motherly Fuckery from the Undertale fandom, Parappa shrinks himself and goes inside Lammy's head, and...well, I'm not even going to spoil how shit ends up going from there; just see for yourself, and be appalled.
Categories: Young Adult 20-29, Giantess, Adventure, Breasts, BBW, Body Exploration, Butt, Couples, Crush, Fantasy, Feet, Furry, Futanari, Humiliation, Incest, Instant Size Change, Lesbians, Maternal, Mouth Play, Muscle, Nose, Odor, Scat, Slave, Unaware, Violent, Vore, Watersports, Teenager (13-19)
Characters: None
Growth: None
Shrink: Lilliputian (6 in. to 3 in.), Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/m
Warnings: Following story may contain inappropriate material for certain audiences
Series: None
Chapters: 6 Table of Contents
Completed: Yes Word count: 19045 Read Count: 30196

Summary:

In what is more than likely THE absolute kinkiest Undertale fanfic of all time, Asriel, after watching way too much Alphys VS Undyne, decides to re-enact the series' infamous giantess Alphyne scenes, only with him and Toriel! Needless to say, things get REALLY fetishistic and REALLY fucked-up REALLY freaking fast; trust me, you have been warned.

Categories: Vore, Giantess, Teenager (13-19), Adventure, Humiliation, Breasts, BBW, Body Exploration, Feet, Furry, Futanari, Incest, Insertion, Instant Size Change, Maternal, Nose, Scat, Unaware
Characters: None
Growth: None
Shrink: Micro (1 in. to 1/2 in.)
Size Roles: F/m
Warnings: Following story may contain inappropriate material for certain audiences
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 9517 Read Count: 10503

Summary: (ORIGIN: Chapters 4-5.5 of HBACSAPS)

Just when you think that Xander's brain fetish simply can't get any worse, this scene (hell, pretty much the entire Grinch-spoofing story that it came from, for that matter) comes along and proves you wrong...and yes, I'm well aware that that rhymed.

Despite being an incredibly great and overlooked fanfic that just so happens to be a remarkably clever and affectionate parody of no less than three different things at the same time (Undertale, xandermartin98's fanfiction library for it, Dr. Seuss' Grinch) with some really phenomenally executed writing and humor (and fap material), I can still admit that this story in particular gets REALLY out of hand with the whole brain thing, with this scene being easily the absolute definitive example.

Personally, I would highly recommend bringing a good amount of brain BLEACH for what ends up happening here; seriously, don't be fooled by the fact that it starts out as a perfectly normal Donald/Hillary election parody speech between Bratty and Catty, because before you know it, the story pulls a lesbian SIX-some on you, with two of those six actually being mutated synthetically cloned pieces of Bratty's and Catty's brains (that Alphys and Undyne are busy having SEXUAL INTERCOURSE with, naturally enough). Obligatory link to full story: https://www.fanfiction.net/s/12320570/1/How-Bratty-and-Catty-Stole-America-s-Presidential-System
Categories: Giantess, Teenager (13-19), Adventure, Young Adult 20-29, Breasts, BBW, Body Exploration, Butt, Couples, Destruction, Fantasy, Feet, Furry, Futanari, Humiliation, Incest, Insertion, Instant Size Change, Lesbians, Nose, Sci-Fi, Unaware, Violent
Characters: None
Growth: None
Shrink: Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/f
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 6328 Read Count: 4706

Summary:

If you want an absolutely PERFECT headcanon for why Katz hates Courage so much in the actual Courage The Cowardly Dog series, look no further than here. Let's see how YOU feel about someone after having that someone go inside your brain without your permission and then use it to completely wreck your entire life while a sadistic Chinese con artist films it on live video, shall we? 

Categories: Adult 30-39, Giant, Adventure, BBW, Body Exploration, Butt, Couples, Crush, Entrapment, Fantasy, Feet, Footwear, Furry, Gentle, Humiliation, Incest, Insertion, Instant Size Change, Maternal, Lesbians, Nose, Odor, Sci-Fi, Slave, Unaware, Violent, Vore, Middle Age (50+), Mature (40-49), Young Adult 20-29
Characters: None
Growth: None
Shrink: Nano (1/2 in. to 2.5 nanometers)
Size Roles: M/m
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 28828 Read Count: 2806

Summary: Blissfully unaware of the wakeup-mushroom-selling potion shop out in the Minish Woods, Link decides to try an alternate, far grosser method of getting the local Hyrule Castle Town shoemaker to make him a new set of Pegasus Boots...why, by shrinking himself to Minish size and sneaking his way into Rem's brain, of course! Please note: this story DOES indeed treat this as a sexual fetish.
Categories: Unaware, Teenager (13-19), Adult 30-39, Adventure, Body Exploration, Couples, Fantasy, Feet, Footwear, Gentle, Giant, Humiliation, Insertion, Instant Size Change, Nose
Characters: None
Growth: None
Shrink: Micro (1 in. to 1/2 in.)
Size Roles: M/m
Warnings: The Following story is appropriate for all audiences, This story is for entertainment purposes only.
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 2186 Read Count: 4259

Summary:

In a sort of between-events sequel to previous Rocko/Maggie crossover fanfic "The Buzz On How Maggie Got Fondled By Flecko" that is SO ridiculously offensive and generally dark/cynical that it actually makes the original story look like freaking BARNEY AND FRIENDS by comparison, Maggie Pesky, after being declared legally insane in the Supreme Court trial that she had found herself being put on for self-defensively murdering Flecko in the previous story, is carted off to the world's most horrifically abusive mental asylum by Dr. Hutchison; to make a long story short, hilarity of numerous incredibly sadistic and generally fucked-up varieties ensues.

You can find the story's predecessor here: http://www.giantessworld.net/viewstory.php?sid=7994

Categories: Mature (40-49), Adventure, Breasts, BBW, Body Exploration, Butt, Couples, Entrapment, Fantasy, Feet, Furry, Giant, Humiliation, Incest, Insertion, Instant Size Change, Lesbians, Maternal, Mouth Play, Nose, Odor, Scat, Sci-Fi, Slave, Unaware, Violent, Vore, Watersports, Teenager (13-19), Young Adult 20-29, Adult 30-39
Characters: None
Growth: None
Shrink: Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/f, F/m, FM/f, M/f
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 1 Table of Contents
Completed: Yes Word count: 56519 Read Count: 4194

Summary: (WARNING: STORY IS FRACKING HILARIOUS)

One fateful night in Parappa Town when Lammy unknowingly sniffs Parappa and Ma-San right up her nose and into her brain while snorting cocaine off of her adorable cat girlfriend's toes, she quickly finds herself deeply entangled in a ridiculously elaborate and immensely torturous mind-control scheme for her band (Milkcan) to be able to join the infamous Joe Chin business so that they can get filthy rich filthy quick. Needless to say, quite a lot of hilarity and gratuitous smuttiness ensue.
Categories: Watersports, Giantess, Teenager (13-19), Young Adult 20-29, Middle Age (50+), Adventure, Breasts, Body Exploration, Butt, Couples, Destruction, Entrapment, Fantasy, Feet, Furry, Giant, Humiliation, Incest, Insertion, Instant Size Change, Lesbians, Mouth Play, Nose, Odor, Scat, Unaware, Violent, Vore
Characters: None
Growth: None
Shrink: Micro (1 in. to 1/2 in.), Nano (1/2 in. to 2.5 nanometers)
Size Roles: F/f, F/m, M/f, M/m
Warnings: Following story may contain inappropriate material for certain audiences, This story is for entertainment purposes only.
Series: None
Chapters: 7 Table of Contents
Completed: Yes Word count: 30568 Read Count: 20970