The Danza: Young princess Eva is played by Eva Allan.
Defictionalization: The exterior shots of Storybrooke's main street are filmed on a real road in British Columbia. The signs on certain shops are covered with a Storybrooke equivalent during filming and removed afterwards. However, some shop owners let the production company keep the signs up permanently partially due to this trope and partially to make less work for the film crew (to erect and tear down the signs every week). The producers also leased two units just for the storefronts. These are kept the same year round, since they were never real shops in the first place.
Dueling Shows: With Grimm, an NBC show that also focuses on fairytale characters existing in the real world, although that show focuses on more obscure characters and creatures from the many, many lesser known Grimm fairytales, as opposed to the more famous and iconic ones in Once.
The Queen's fans are called Evil Regals, Snow White's are the Fairest, the Seven Dwarves' are Team 7, Prince Charming's are Charmers, Ruby's are Little Reds, and Belle's are Beauties. Emma's fans were originally called "Team Emma" though "Ugly Ducklings" is becoming more popular.
I Knew It: Mr. Gold perfectly remembers being Rumplestiltskin. Most fans probably guessed it from a mile away, though The Reveal was no less satisfying.
Surprise (or not)! Cora is the Queen of Hearts after all.
Several people guessed as early as last season that Henry's father (Neal) is Baelfire.
The Other Darrin: It seems to be intentional. In Season 1, the Queen of Hearts is played by Jennifer Koenig. In Season 2, she's played by Barbara Hershey when she's revealed to be Cora. It should be noted that even when she was played by Jennifer Koenig, Barbara Hershey supplied the voice, which was hard to make out due to her speaking only in whispers.
In season 3, Sean Maguire replaces Tom Ellis in the role of Robin Hood.
Apparently they wanted Lady Gaga as the Blue Fairy.
The Sheriff was meant to be Sherlock Holmes, and his curse in Storybrooke was that there was no mystery to solve. The plan fell through due to an issue with acquiring the rights. Not to mention the fact that there are already twoSherlocks on TV right now.
Ariel and Aladdin were planned for the second season, but their appearances got "pushed back" for unknown reasons (which means they might appear in Season 3).
Early drafts of the pilot episode had Charming killed off. This was changed after Josh Dallas auditioned and "blew them away" with his performance, prompting the creators to expand his role.
Early drafts also had Regina with three children instead of just Henry, but the identities of the other two are not yet known.