Damian/Kris

Kris used to prank Noelle by scaring her. They tried to summon a demon with Catti. They literally share their body with an otherworldly being. Rudy straight up calls them the "creepy kid next door". They have a knife.

Chara has a "scary face". They laugh off distressing situations. They came up with a horrible, violent plan that lead to both their own and their brother's deaths. After a murder run, they go from concerning implications to fully embodying the Creepy Child trope. Literally having been revived from the dead. Calling themself a demon. You even sell a SOUL to them. They have a knife.

But,

Kris is also a pianist. A hobby they clearly care deeply about, to the point of embarrassment if someone catches them playing when they're not expecting it. They play video games. Their favorite food is butterscotch-cinnamon pie. They eat moss and say and do plenty of goofy shit.

Chara liked to draw. Their knife is described as "perfect for cutting plants and vines", implying that it was for gardening. They liked to fill their cup to the brim, because it was more "efficient" that way. Their favorite number is nine, because there isn't a number that's higher. They want to be the strongest, because nothing can hurt them if they're strong enough.

The golden flowers and buttercups in Undertale are NOT meant to be the same flower.

GOLDEN FLOWERS

-Chara said that these were the flowers they wanted to see from their human village, but there was "nothing [the monsters] could do", implying that these flowers weren't available Underground before their death.

-The flowers get transported there because the seeds are sticky, they got stuck to Chara's body because Asriel rested them in a bed of golden flowers before bringing them back.

-Safe to consume, Undyne has a pack of golden flower tea and they are also stated to be Asgore's favorite.

-This is what the flower bed at the beginning of the game is actually made of, which we know because if you backtrack after the first Flowey encounter and inspect them the narration says "Golden flowers. They must have broken your fall."

-Probably what Flowey actually is.

-Likely a fictional species of flower, hence the weirdly nonspecific "golden flower" name.

BUTTERCUPS

-These were available in the Underground, we know because Chara and Asriel poisoned their dad with them (accidental) and then Chara poisoned themself with them (intentional).

-As per the last bullet point, very much NOT safe to consume.

-An actually real species of flower.

WHICH THAT BEING SAID, Deltarune does seem to be conflating the two...

-Flowery is presumably based off of the same kind of flower as Flowey, but...

-Kris obtains a packet of golden flower seeds, with warning labels on them.

-HOWEVER, this could be a case of Deltarune being an AU, and therefore the details can be fudged a bit sometimes.

-OR golden flowers could be one of those plants that have poisonous seeds while the flowers themselves are safe to consume.

-Hell, we technically don't actually know if they're poisonous. The warning labels could be about them being a choking hazard! We also don't know if Kris even actually plans to use them on themself. It's too early to really say for sure.

-However we do get a reference to buttercup pie earlier in Chapter 5, so on some level we're supposed to be reminded of Chara.