Most of you probably notice that when you fight multiple mimics, they usually throwout a random line once you KO the first: “We can sense the fear in you…” being one, for example.
However, as you ALSO might know, the “real” version of characters can show up as well, depending on your actions during a mission.
To give an example, I did the “Assault on The Carribean” mission, which gave me a pre-mission option to say hi to Spinal or ignore him. I chose the former, which then inserted him into the fight as a challenge.
After I defeated the Mimic, Spinal appeared and said this line. Not entirely sure how the bug is caused, but that’s usually how it happens.
TLDR: A mission where a non-mimic character appeared because of a mission option said a mimic line before I fought them on the versus screen.