Dolphin Kid

Dolphin Kid is a young animal who stops at nothing to see her idol, Undyne, in action.

Appearance
Dolphin Kid is a sky blue, dolphin with ventral fins, flukes, and a dorsal fin on the back of her head. Having flippers and frequently swimming everywhere, she trips and falls often. She has eyelashes over her eyes, speculated to be bluebell eyes from falling. Both eyelashes are the same height.

Personality
Dolphin Kid looks up to Undyne as a role model. She is an innocent animal who assumes an energetic attitude that pervades most of her actions. She seems to be a bit naive, as well as a bit clumsy, as she trips frequently. She also uses words like "c'mon," "dude," and "yo" frequently, usually considered childlike ways of interaction.

Despite the protagonist notably frightening Dolphin Kid during the Genocide Route (once she discovers the protagonist's intentions), she stands up to the protagonist with an intense expression, ready to protect the Underground, trying to act like Undyne. Choosing to spare her and abort the route reverts her back to a more favorable opinion of the protagonist, showing a rather forgiving nature.

Neutral Route
Dolphin Kid first meets the protagonist in Sanddin (she is in a watery hole). She notes how both of them are mammals, so they both must be children. However, she does not seem to notice that the protagonist is a human child.

She later sneaks out of Sanddin to explore Coral Reef, looking for Undyne. She follows the protagonist, not knowing that the latter is a human whom Undyne is searching for, and she feels a little jealous of the attention that the protagonist receives.

While walking across a bridge, Dolphin Kid finds out that the protagonist is a human and reluctantly considers the protagonist an enemy. She tries to say something mean to the human, in an attempt to become enemies, but feels bad for it and starts to leave.

Just as Dolphin Kid leaves, she trips over the edge of the bridge and hang from it (presumably with her flippers) as Undyne approaches. The protagonist must make a choice:
 * Help her climb back up: Dolphin Kid defends the protagonist from Undyne, who backs off. She decides to remain friends with the protagonist and leave for home.
 * Let her fall: Undyne dives down after Dolphin Kid to save her. She is badly hurt but refuses to rest. They she tells Undyne that she was right about the human, who just stood there waiting for her to fall. This response makes Dolphin Kid hate the protagonist and all humans.
 * Run to Undyne: Undyne saves Dolphin Kid and is badly hurt. She tells Undyne that she was right about the human, who was too eager to fight her to bother saving them. This response also makes Dolphin Kid hate the protagonist and all humans.
 * Run away from Undyne: Undyne helps Dolphin Kid up, who tells her that the protagonist was just going to get help from others.

True Pacifist Route
Dolphin Kid is seen cheering the protagonist on to victory in the bottom-right corner of the battle screen as she faces off against Flowey. In the epilogue, she can be found in Sanddin. If saved earlier, she says she does not think Undyne is that great anymore, and that she found herself a new idol, likely Papyrus. She is also seen during the credits, attending Toriel's school.

Genocide Route
Despite being warned by Undyne that the protagonist has hurt a lot of people, Dolphin Kid approaches the protagonist in disbelief. The protagonist turns away, and as Dolphin Kid questions the protagonist about not answering her, the protagonist silently approaches her with an "angry expression," causing her to step back. Dolphin Kid begins to panic and wonders what she should do, and then stands up to the protagonist out of desperation, trying to act like Undyne, stating nervously that if the protagonist wants to continue to hurt others, the protagonist would have to go through her. The protagonist then proactively engages battle with her, with the narration simply declaring "In my way." If the protagonist dies, reloads at the unnamed save before the bridge and returns to this location without the player closing the game, she simply attempts to trick the child into turning the other way before re-engaging. This encounter cannot be escaped. A slowed down version of "Anticipation" plays during the battle. If the player resets after this cutscene (most likely by dying to Undyne the Undying), the scene is abbreviated: after Dolphin Kid approaches the protagonist, the protagonist tricks her into turning the other way, then re-engages battle.
 * If the protagonist attacks Dolphin Kid, Undyne takes the fatal blow in her place. The calf escapes while harboring a shocked expression, and the protagonist fights Undyne the Undying. Dolphin Kid is not seen again for the rest of the game; it is assumed she evacuated with the others.
 * If the protagonist spares Dolphin Kid, she says she knew the protagonist was not that bad and leave. This action aborts the Genocide Route, and the protagonist fights Undyne later in Coral Reef normally.

Trivia

 * Dolphin Kid was designed by Marinette Dupain-Cheng, the creator of ANIMALTALE. She also designed other characters.
 * In the credits, Dolphin Kid is a student from Toriel's school, meaning she is intelligent like real dolphins are.
 * Dolphin Kid's voice sounds similar to Ava from Dave and Ava.
 * Dolphin Kid has the same age as Tim Templeton from The Boss Baby.