look at this cat

The Boss Monsters from Undertale, and by extension Deltarune, are partially inspired by Mimiga.

Ralsei, the prince from the dark, is inspired in-universe by the Boss Monsters that make up Kris's family.

Ralsei is doomed to get wrapped up in some flower situation while in the field of pink and gold, as evidenced by a combination of early merch involving Ralsei and flowers as well as his indirect connection to Flowey.

Do not let this poor little prince cross paths with the red flower, it won't end well.

But seriously what if the final tragedy of the Delta Rune is Ralsei eating red flowers and becoming feral

This absolutely won't actually happen and I'd be shocked if it does but considering how far the roots go back (pun intended) there's surely some sort of inspiration connection?

Flowery.

The fact that Flowery got the Zero treatment made me actually cheer though.

Even though we learned more about his character and he became sympathetic, I still cheered for the Roaring Knight.

Homestar Runner - Strong Bad's had his time in the sun, let's get the main guy in there.

Stanley (with the Narrator) - I can imagine it now: "Stanley had a high card. That was the best he could do, and from the faces of everyone else around him, he knew what must be done, so he folded. ...Stanley, why did you just go all in? STANLEY! You know you can't afford this! Why did you bet everything?!? YOUR HAND IS TERRIBLE! The bucket is ashamed, you know. Ashamed." He could keep his chips in the reassurance bucket and everything.

Xavier: Renegade Angel - I saw this suggested somewhere else and I think it would be just what the game needs.

A TADC character, likely either Pomni or Jax - That wouldn't be too hard to pull off, I'm certain. They could just handwave it as them thinking it's one of Caine's adventures. Alternatively, it's Caine as a dealer, like in Poker Night 2 with Glados.

Wheatly - We already have Portal representation, I demand more. Or Chell. Why not. Silent, great poker face. Gordon Freeman could work too, in that regard.

Toby Fox voicing John Egbert - Preferably in the same game as Homestar Runner, so we can have them meet. Because that would be a historic moment in itself. And they had Penny Arcade guy there, it's not a big leap.

Dynamite Anton, Antonblast - He's fully voice-acted anyway and would be a good pick, I think. Either him or Annie. They even collect chips in the game as currency anyway! Heck, make Brulo the dealer.

Jimbo from Balatro? - Why not. Though, as far as I'm aware, he doesn't have a proper voice?

Just stick a YouTuber in there. Markiplier or something

Baldi from Baldi's Basics - I just feel like they'd make some really funny situations if they added him.

Hat Kid - "Why are they letting a kid gamble?!?"

Charles from Henry Stickmin - (Goes all in) "This is the GREATEST PLAN-" (Loses everything)

Jesse from Minecraft Story Mode - Get the licensing back. Get those games remastered too. Just do it.

If they can find a voice for him, Zacharie from OFF - He's probably be a good dealer.

Poker Nights at the Inventory