Unexpecterchanged Flowey has the appearance of a golden flower, but is very faded and dissheveled from lack of self-care and isolation. He has an almost permanent smile on his face, and bags under his eyes.
Unexpecterchanged Flowey is antagonistic from the first time you meet him. He is shown to be cold and apathetic, from the way he leaves Frederick for dead instead of killing him outright. He likes to tell terrible plant puns and jokes, but the only one that laughs at them is himself.
Flowey is first met in the Ruins, where he is shown greeting Frederick. After a few plant puns, he teaches Frederick how SOULs work in battle. Almost immediately after, he sprouts up an undodgeable attack, leaving Frederick with 1 HP. Instead of killing him, he leaves Frederick to wander the dark, cold RUINS alone. Flowey shows up once again at the end of the long hallway, taunting Frederick while leaving a vague hint about Chara.
Flowey shows up one final time at the end of the RUINS, giving Frederick a choice of "Leave or die?". When Frederick responds with "Leave", Flowey takes it as them answering as "Die" anyways and starts a battle. Flowey attacks with a combination of vine arms and friendliness bullets. When his attacks are repeatedly dodged, he starts to lose patience. He slowly becomes more aggressive until he suddenly calms and announces his "special attack." He builds up to his special attack for multiple turns, even using a one-pellet attack right before it. This attack is undodgeable.
After a RESET, Frederick confronts Flowey again, where he shows his knowledge of resets. He starts the battle a second time, but goes straight to his special attack. When he is confused by Frederick surviving his special attack, he is attacked from behind by Chara. He manages to get away with 1 HP. Chara and Frederick escape the RUINS through the locked door that was destroyed by Flowey's special attack. Flowey's whereabouts are currently unknown.