Sandshrew is from Lairette on GameFAQs. I'm friends with her. :)
https://www.gamefaqs.com/community/Lairette/bio
Gible is from the GameFAQs user with the same name.
https://www.gamefaqs.com/community/Duhveed/bio
Jangmo-o... Let's see if someone else can confirm this, because I'm a bit rusty on Egg Move breeding.
Jangmo-o was hatched in December, a month and a half before Pokebank was out. Which means the Egg Moves must be from Pokemon in the Alola Dex. The Jangmo-o has 3 Egg Moves + Dragon Dance. I forgot how Egg Move breeding works, do each Egg Move Transfer, or do all 3 need to be from the same parent? One possibility is that the OT kept breeding each Egg Move onto it to create the perfect Shiny Jangmo-o, but I believe the stronger possibility is that someone hacked a non-Alola dex Pokemon in and bred for the Jangmo-o. Or it's just straight up hacked/illegal because it has all 3 Egg Moves. Hopefully someone can confirm or review this.
Mimikyu and Mareanie. Judging by the topic, you got it from the original owner, themoonblaster. I'd say that's legit, I haven't heard of that person being a hacker or anything.