Mainly TEP headcanons

The Bois headcanons

The duos bonds and what they were like (and how they bonded)

Fell used to shut others out because he was scared of hurting the people that he cared about, thankfully Ash is helping him open up to others so far Davis, Tom, Riku know about some personal stuff (the others do know about Fell's cannibalistic side so they know the precautions to take when Fell goes mad, more on that soon in the undertale headcanons chapter)

Abby and sollux both have anger issues. Sollux grew up around toxic trolls and being a low blood doesn't help, he lost his cool once and slammed Vrisca's head on a wall after she pushed him a little to far he's one of the strongest of the low bloods and is respected by some of the high bloods, Abby grew up being made fun of and had to always fight to keep people from hurting her and her brother the two often help each other with there anger so far only Fell and Davis knows about there anger

Riku and ennard have hidden a lot of secrets from others and these secrets often hurt themselves, they've only told the others a little bit of secrets but so far the two know about their hardship secrets (excluding Michael since he's practically connected to Ennard)

Tom and todoroki both have family problems Tom's been abused (mentally and verbally sometimes physically) and neglected while also being bullied, while Todoroki has a strained relationship with his dad and an iffy relationship with his mother (yeah- we all know why), Todoroki and Tom vent out about their family issues to the other and are each other's shoulders, only Fell and Ash know about their situation

Michael and Davis both shut out their feelings from other people as they don't want to burden people with their problems, no one but two knows about how they really feel (minus Ennard, since Ennard is practically connected to Michael)

Speaking of shutting out feeling when any of the others felt down they usually to be able to get away with saying "I'm fine" to the others, but as time drove on the other half of the duos would see the lie and it never seemed to work on that person, so that's when all of that (from above) happens

When the Bois are sick:

When Abby gets sick she sits around a lot and is surprisingly not stubborn when it comes to taking medicine

Fell never gets sick, like ever (lucky bi-)

Sollux acts a little dramatic and hates taking medicine (the others have to force him to take medicine)

Michael can't get sick cause they're dead. Ennard also can't get sick, cause they are an animatronic

Riku doesn't get sick often when he does he acts clingy and doesn't care about the medicine

Tom hardly gets sick cause of his demon but when they do it's pretty bad he will sometimes end up with a power serge but it won't hurt anyone, will eat all the medicine if he has too (he hates being sick)

Todoroki also hardly ever gets sick cause he uses his quirk to fight off any of the bacteria, but when that doesn't work he sleeps a lot and only gets up to take medicine, get something to eat, or go to the bathroom Tom usually keeps an eye on him in case something happens he doesn't care about the medicine

Davis often rambles when he's sick it tends to annoy the others but a select few, to be honest when Davis rambles he's a lot more honest and doesn't fuss about the medicine

When Ash gets sick it can be either pretty bad or mild no in between, he stays in bed a lot and either doesn't care about medicine or flat out refuses to take it (someone's gotta force it down his throat sometimes)

Headcanons:

Fell and Tom are both cannibals, Tom to keep his demon at bay and Fell cause of survival reasons (more on that soon in a undertale headcanons chapter)