(This will be separated by character, it will make sense as you read.)
Undyne's fan
Fan: Hi, Undyne...*Meekly walks into room*
Undyne: Hey, punk!
Fan: *sits down next to her* S-so.....I'm here with you.....
Undyne: *looks to the left* *looks to the right* *looks back at them* I think so!
Fan: W-wow.... I didn't think this would happen...*blushes*
Undyne: Well, it just did, NGAH! *lifts random table for no reason*
Fan: *eyes light up* WOAH!!
Undyne: HA! You're impressed with something as light as that?
Fan: *nods amazed*
Undyne: *laughs* You're weird like Papyrus.
Fan: *giggles*....OH! Uh....can you....uh....um...
Undyne: SPIT IT OUT!
Fan: C-can you sign th-this. *holds up picture of her*
Undyne:....Me?
Fan:.....Y-yea--
Undyne: OF COURSE I CAN, NNNNNNGAAAAHHHHH! *Aggressively signs photo* *le pen breaks*...Oops...
Fan: *doesn't care about the deceased pen* THANK YOU *runs away*
Undyne: You're welcome???
Alphys' Fan
Fan/Alphys: *sits in the room staring at each other awkwardly for 40 minutes until they both run out screaming*
Papyrus' Fan
Fan: *gasp* OH MY..... IT'S Y-YOU!!!!
Papyrus: NYEH?
Fan: OH...OH DEAR... I DIDN'T PREPARE MYSELF... U-UH.... I'M LIKE YOUR BIGGEST FAN, I DON'T EVEN KNOW WHAT TO DO I-I...Ummm *blushes* Aw, geez, I'm being stupid, I should just leave... *tries to walk away*
Papyrus: WAIT! DID YOU SAY FAN?
Fan:....Y-yes...
Papyrus:... WOWIE! I HAVE A FAN! THIS IS THE BEST DAY OF MY LIFE! *Runs over and hugs the human* IT IS SO NICE TO MEET MY GREATEST FAN, NYEH HEH HEH!
Fan: *blush intensifies*
Papyrus: HUMAN! YOU'RE FACE IS TURING RED! LET ME GO GET YOU WATER! *goes to get water*
Fan: hnnnnnnnn *dies from happiness*
Toriel's Fan:
Fan: *gets showered in motherly affection and butterscotch-cinnamon pie*
Asgore's Fan:
*The two have a nice cup of tea together and do some gardening*
Mettaton's Fan:
Fan: *dies upon meeting him because his fabulous levels were too high for them to handle*
Frisk's Fan:
Fan: Hi, it's so nice to meet-
Frisk: *has flashback to the fanart of themself from the Frans ship* I DON'T HAVE BOOBS!!!!! *runs out of room screaming*
Fan:.....Erm...
Chara's Fan:
Chara:...Why do you like me again?
Fan: I-I just think that you're n-nice...
Chara:... Really? Someone thinks I'm nice....heh, that's new.
Fan: A-a lot of people think you're nice...
Chara:...Wow... humans sure are odd...
Fan: Are you okay, you seem distracted....
Chara: Oh me? Just thinking to myself, that is all.
Fan: O-oh.... I guess I should l-leave then...
Chara: You don't have to if you don't want to, I'm just... distracted I guess...
Fan: Oh... well, I just wanna do one thing b-before I go... *quickly hugs Chara*
Chara: *brows furrow* What are you--??
Fan: We aren't all that bad... I promise.... *quickly pulls out*...Erm.... I guess b-bye! *runs out of room*
Chara:.......*awkward smile*...Goodbye...
Jerry's Fan:
*But nobody came...
Sans' Fan:
Sans:....uh.... are you gonna say something...or move at all.... you've been standing in the doorway for like ten minutes....
Fan:.....
Sans: i've talked to myself before, but this is just weird...
Fan:......
Sans: *whistle* yoo-hoo? anyone in there? *waves hand in front of their face*
Fan:....
Sans:....i'm just gonna....leave the--
Fan: NO WAIT! *covers own mouth*
Sans: hey look! you said two words, congrats.
Fan: *covers face blushing*
Sans: what's up with that expression?
Fan: *mumbles something*
Sans:...huh?
Fan:......You're short and I can't handle it.... *blush intensifies*
Sans:.....
Fan: S-sorry! You're just...so...little a-and... GAHHHHH! *throws hands up dramatically*
Sans:......
Fan: Oh no, are you angry? I-I didn't mean it in a bad way, I-I just-
Sans: *laughs* nah, kid, your fine.
Fan: Really!?
Sans: yeah, you see, everything just kinda goes right through me. *winks*
Fans: *giggle*
Sans: ya like jokes, ay? 'cause i got a skele-ton of th--
Papyrus: *breaks down door* SAAAAAAAAAAAAAAAAAAAAAAAANS! *grabs his brother* *runs out of room with him above his head*
Sans: *slowly getting quieter as he gets farther away* lookslikeigottagoseeyaaaaa...
Fan:..... *screams to themself*
Flowey's Fan
Flowey: *chases them out with friendliness pellets* F*** YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Fan: I DIDN'T DO ANYTHINGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Toriel: PROFANITIES ARE BAD!!!!!!!!!
(I don't even know what this is....)

YOU ARE READING
Undertale Characters React to Ships
FanfictionOkay, so basically, I'm going to try to take any canon clues I can find to come up with their reactions to the ship. It will follow the same order as my own opinions if you want to compare or something, xD. But this is all for fun! I don't even know...