I think the person Undyne remembers in her fight is more likely to be Asgore, especially considering she later makes this comparison between the player and him.
lightlunas replied to your post “Hey, something interesting just happened to me. After a few months of...”
I always thought this was about Asgore, since I imagined he would have said something similar the first time Undyne tried to fight him, trying to calm her down with that
kitkqtenderheart replied to your post “Hey, something interesting just happened to me. After a few months of...”
The someone could also be Asgore, as she directly mentions that they remind her of him during the date
Note: This is a follow up to a previous ask about this flavor text.
While Undyne does make a comparison between Frisk and Asgore in the battle after her hangout (”You’re a wimpy loser with a big heart! Just like him…”), this comparison is specifically about Frisk’s kindness. During her boss battle, it’s more likely that Undyne remembers Papyrus when Frisk says they “just want to be friends.” As previously stated, the reason for this is that Papyrus is adamant about making friends!
Regardless of how Frisk responds to Papyrus’ question, he will readily befriend the human.
Seen when Frisk says “no” to his question “Are you wearing X?” and does not switch clothing.
Seen when Frisk says “yes” to his question “Are you wearing X?”, then switches clothing.
This desire for being friends with both Frisk and Undyne is likely why Papyrus is adamant about the two becoming friends as well!
Unlike Papyrus, however, there is no mention about Asgore having such a strong desire for friendships or asking Undyne to be friends. Instead, he offers to train her. Undyne likely sees Asgore more as her mentor rather than friend.