MLP X WCMI CROSSOVER THINGS THAT NOBODY ASKED FOR IN NO PARTICULAR ORDER
Twilight and Alice would be instant BFFs!!! Twilight is literally like the pony version of Belle so Alice would obvi instantly form a friendship with her. Alice would love Twilight's old library treehouse! And maybe they would also bond over the fact they were chosen to become royalty (in the original through the looking glass book Alice did become a queen so technically Alice is royalty and she hangs around the Disney Princesses even tho she's not in the Disney Princess line up she's still considered a poster child for Disneyland)
Reginald would be BFFs with Pinkie Pie. And also Cheese Sandwich later on. But guys IMAGINE REGINALD AND PINKIE ARGUING ABOUT BIRTHDAYS/UNBIRTHDAYS!!! The irony of these two crazy party loving idiots arguing over which is better?!? Pinkie's literal job is to remember everybody's birthday and host the best parties in all of Ponyville. Sweet Celestia! She even inspired her future rival/husband Cheese Sandwich to become a travelling party pony just like her. Now imagine Reginald the mad man of tea parties creating an even crazier UNbirthday party just to prove who is better. It's a friendly competition but still.
Alice would think Celestia's Castle is reminiscent of the castle at Disneyland. Same for The Crystal Empire Castle. Twilight's castle tho ehhh not so much...
Alice and Reginald would have tea parties with Fluttershy and Discord. Alice would prefer to have the parties at Fluttershy's cottage but Reginald would prefer Discord's topsy turvy dimension. Basically the Discordant Harmony episode vibes.
Reginald would bombard Doctor Whooves with time puns just like the Johnny Depp Hatter did to Time in ATTLG. Mad man in a big tophat meeting a Mad man pony in a big blue box
Alice and Reg would LOVE Derpy Hooves. I mean who doesn't? Alice and Reg basically adopt her. She is their honorary daughter now. She has Alices hair color and curiosity. She has Reginalds short attention span, dumb ditzy personality, and both are surprisingly very good at their jobs. Reginald would have special muffins just for her at the tea parties.
Whenever Alice hears Princess Luna do her Royal Canterlot voice she gets flashbacks of the Queen of Hearts yelling Off with her head
That's all from the top of my head so far. Feel free to add more I guess??