Probably not the worst things I've ever done on here but these come to mind.
Years ago I name-changed a pet to something else then a couple years later I decided I wanted the original pet name back so I recreated it. Basically wasted csc for a pointless name change lol.
I also worked to gather enough steamwork trinkets to get a key to make a steamworks pet... but only for the achievement of having a steamwork pet. I changed the pet to something else afterwards. Now every time I consider a new steamwork pet I'm reminded of how wasteful I am. :P
I just changed my favorite pet, my battle pet Bae In Toyland, to a nostalgic ontra because I was not paying attention. Now my poor little Bae is an ontra!
Oh! Tag me in coach, I got a good one!
Came back form hiatus to several loyalty boxes (this is a few years ago). Wanted to change a pet to glade, so I decided to use the colour change totem (first mistake). Soooooo in all my brilliance I went ahead and changed my poor darling Clifton into a... field kora. Not a glade kora, field (second mistake).
Now, unsatisfied with my new field kora, I decided hey, I have more of these totems! Might as well make him glade and get it right this time! So, another colour change totem (mistake three, sigh) and I finally have a glade kora!
And now that's two pet slots I'll never have and also I didn't even keep Clifton a glade kora ANYWAYS.
[flower=trithie]
I did the same thing too, but I just wanted to feed it something for the gourmand achievement, not even realizing that it would change my pet species.
I didn't realize doing the quests in the blue building turned my pet into a bumbus lol
Accidentally turned my first pet into nostalgic from graveyard because I wasn't paying attention. I think I assumed there would be a drop down menu of the pets to choose from
Main Cosplays: Harley Quinn, Captain Marvel, Elsa, Mera, & American Dream
Recently I accidentally read a Tome to my pet, and the worst part is that he complained about it. A little before the snowman contest, I spent 40m in a pet slot. Since then doesn't matter how many pets I create Subeta finds a way to give us more and I end up with an extra slot. Categorized an entire page in the wardrobe and refreshed it afterwards thinking it was like the vault (I knew it wasn't, I just retarded for that split second). Used to buy CSC cheap and sell it later for a higher price, the problem being that this "higher" price was ~3.5m. Now I don't sell whatever I'm able to get even if my life depends on it.
Pretty sure I could write a book but these are the ones I remember. [sub]Bonus: right after finishing writing this the lights went down[/sub]
Hahahah, I love how this turned out, everyone is in the same Titanic after all.

I do not love you except because I love you;
I go from loving to not loving you,
From waiting to not waiting for you
My heart moves from cold to fire.
- I thought you meant in general because on friday I ran over a frog with the lawn mower ;A;
On here in recent years. I tried to transfer a pet through the AC, because I lacked patience, and I lost it :(
I fed a gold shop wearable that was also a food to one of my pets once. Fortunately, it was during a clearance sale so I was able to get it again without too much pain.
I just did something stupid :x Went to the Blackheart Hollow, and then absentmindly... didn't scroll all the way down, and closed the window... but I thought I saw something weird out of the corner of my eyes when I did. Oh! There was actually an item! :o Crap. Open the window back up. Try to click buy.... too late, it was gone... :( I have done this once before as well. ;p
Apart from this, I would often open up Subeautique or BHH and totally forget to check. And then I would remember, come back only to see what awesome items I missed...
[font=monaco]« I don't know where I'm going from here, but I promise it won't be boring. »[/font]
🍂🍁🪭
🍭🍬 🥚[egg=Selphina]🍳 🧻[tp=Selphina]🗞️
💋💕 🌸🌻 💃🕺
Oh nooooo! I've never seen an item in Blackheart Hollow :( That's bad...

I do not love you except because I love you;
I go from loving to not loving you,
From waiting to not waiting for you
My heart moves from cold to fire.
I have zapped Snape SO many times because he is my main pet but luckily now I don't zap too much xD But I believe that I have sent things to frozen/inactive users by accident before. It usually happens when I call people by their real names because their friends and when I go to send an item to them, I send to that name instead of their username. :p
Dexter by ❤
Even though Ji is my active pet, she does not appears as first option in the zapper list, I'm always confused, haha About the items, I always do this on purpose when it comes to the major drills quests, hahahaha

I do not love you except because I love you;
I go from loving to not loving you,
From waiting to not waiting for you
My heart moves from cold to fire.
a couple of weeks ago i spotted a steamwork pet in the pound. i figured i could quickly adopt it and then abandon it for the achievement, but i was already maxed out on pets. so i looked through and decided i would be willing to risk pleonastic - if someone snagged him while he was in there, i wouldn't be torn up about it.
i forgot that i had recently added a few things to his tc. as in, several dozen million sp worth of things.
i also forgot that abandoning a pet deletes all its treasure items.
well, he didn't get snapped up so i figured i'd just take him back after my business was finished. then i realized what i'd done. cost me a pretty penny to restore it.
I deleted a whole shop full with CSC collection items (3 pages) I was about to sell (afterwards I could laugh about it and I still do) (:
Ouch! It's good to share these things, for example, I didn't knew the thing about the treasure items getting deleted in the pound :O We can all learn from mistakes... hahaha after all, it's all we can do.

I do not love you except because I love you;
I go from loving to not loving you,
From waiting to not waiting for you
My heart moves from cold to fire.
Oh god, I thought of some from reading others' responses.
In addition to zapping the wrong pet (did I mention he was Spectrum?), I've also
I'm sure there are more, I am VERY absent minded and unobservant. ^^;
I totally didn't know this either, I thought the treasure items went with the pet like the minion does...
It was definitely a while back, but I decided to change what pet I was zapping at the time... forgot to take off her minion, and the minion got zapped. I don't remember the minion, but it was an expensive one x.o
I try not to think. It interferes with being nuts.