I know I should probably watch wonderland before asking this question, but does season 6 of OUAT relate at all to the Wonderland spinoff. I seen comments saying it doesnt at all. Or at least they have recast everyone. Though based on cast it looks like Wonderland never had Aladin and Jasmine only the Genie and Jafar, so I am very confused.
It connects and is canon. Jafar is the same Jafar (although played by a different actor). All the backstory about Jafar is on Wonderland, including why he was a genie in 615. Also, Dr. Lydgate and the Victorian England world that was in 604's flashback appear in the spinoff, because it is Alice's home world, and she is one of Dr. Lydgate's patients. Also of note: Will Scarlet from Season 4 is a main on Wonderland, and Robin, Little John, Friar Tuck, Maleficent's voice, Cora, and the Catapillar all appear on Wonderland. Jefferson is mentioned. Leroy and Ashley have a quick cameo in the first episode. And SB is seen for a bit. Overall the stories are seperate, but they are canon to one another. I suggest watching the show, because it is a cool story in the Once universe, and shows off lots of characters from Alice's Adventures in Wonderland and Through the Looking Glass they didn't appear on the main show.