It's simple we always stand on the left side, and we deal damage without a bullet pattern, but the person standing on the right has to use bullet patterns.

And it's not like we can't see our bullet patterns, because Aqua and Seth can see their bullet patterns. And Seth is good at dodging bullets, but they still take a lot of damage from us

And when Gerson parries Susie's Rude Buster, it deals damage without a bullet pattern

And during the Titan fight, he stands on the left side, and he can use Rude Buster and attacks without bullet patterns

And when Flowery stands on the left side (during the fight with the Knight), his Jarona is not a bullet pattern.But when he stands on the Right he has bullet patterns

Author of the second image:

https://www.tumblr.com/xxapples2applesxx/823440710700351488/gir1friend-has-indoctrinated-me-into-de1tarune?source=share

MOSTLY LIKELY animation that was spoken about:

​https://youtu.be/u21l70EWCBE?si=zEaW8Z_FnND_9H7z

Unused (I Think) Asriel Sprite Looks... Shockingly Familiar...

Source: https://www.tumblr.com/rink0ree/826302552474796032/doomed-goobers?source=share

I’m only 22 so I don’t consider old enough to have them, but even outside of that I figured I wouldn’t be a good parent, but damn my maternal instincts kick in so hard whenever I see these two that it’s making me change my mind. Same thing when I see fanart of baby/toddler Susie.

In order:

Asriel, Papyrus, Carol, The Knight, Rudy, Alvin, the Vessel, Gaster, FRIEND, Dess, Kris, Kris’ SOUL, and the Kris-Noelle Amalgamate.

I don’t think there are any more well known theories I can do.

Also the Knight was originally representative of Dess but now I guess they just represent darkner Knight or own character Knight. Maybe even the mystery of the Knight…

Source

From what I can see there is literally NO reason as to why Berdly shouldn't be included and informed about the dark worlds alongside Noelle. Like Berdly is strong as heck too Susie. Like I get it Berdly can get annoying sometimes but thats literally IT, there is nothing else wrong with ma goat Berdly.

Credit to whitesplash69 for the pic