Puck lovingly treats Emilia as his daughter and generally acts as a father figure for the half-elf. In loops where Emilia died, Puck goes on a rampage, claiming that the world is worthless to him without her in it.
Puck has a positive friendship with Subaru, likely stemming from the boy's friendship with Emilia. However, in a loop where Subaru accidentally killed Emilia by telling her about Return from Death, Puck angrily froze him to death for breaking his promise with Emilia, returning to the mansion against her wishes, and being the one that killed her.
Puck seems to be acquainted with Hector, as he mentioned that Roswaal L Mathers could never become a warlock.