My best friend had pet fish who kept dying off - but she never knew it. Her mother would replace them with an identical pair each time. Then the pet store ran out of those precise fish - the only ones they had were a far larger version, and the mother was terrified she'd see the difference. Cue friend coming home - "They grew!"

When my mom took my computer and [=iPod=] and told me I couldn't have them back until I finished my missing homework, I tried to substitute my stuffed turtle for my beloved Companion Cubes. It worked (sort of).

This troper's friend claims to have another friend with a goldfish, whose mother would tell her to distract said friend whenever the fish died so she could replace it.

This troper had one friend who he used to hang out with, and have over the phone RPG's with. We were like brothers, and in truth, it was a brotherly bond which I wanted. Said friend moved away, and queue me looking around for people to basically use as replacements for him. Some were more successful and others were less. It was taken to disturbing Jin Kisaragi level clingy behavior once, thankfully, I have recovered.

I feel like I became this for a friend over the internet many years ago; her boyfriend had stopped logging in a very short time before I met her, and she had told me on more than one occasion that something I said, did, liked, or disliked was the exact same as said missing boyfriend. As far as I can tell, this resemblance was probably the only reason she was even able to tolerate me.