Sinister Calling Achieve - bugged?

[Boosa-westfall]

"Sinister Calling" achievement is currently unobtainable on Alt characters

So this year I’m working on getting the Hallow’s End achievements on my alt since I did not do them on that character last year. I did however do them on my main character and ended up getting the sinister squashling pet on him. With the new ICC patch rolling out, Mounts and companion pets are now shareable on all your characters. Today I did the Headless horseman dungeon on my alt and received the Sinister Squashling pet from the loot pumpkin. However, it said that I had already collected this…

Please help push this thread that was already started. We need to be the squeakiest wheel to get the grease.