'Once Upon a Time' is a popular running show on American television that features a combination of real and fantastical characters, it maintains a massive viewership all across the globe.

The show has been running for three seasons and the fourth installment is scheduled to come out sometime soon. Some of the spoilers for Season 4 suggest that the television series will witness the introduction of a number of new characters.

Elsa, Kristoff, and Anna, who are well known characters in Disney's 'Frozen', are going to be seen in 'Once Upon a Time'. This has greatly delighted the fans of the show who have been craving for a development like this.

Beyond that, spoilers mention that Queen Arendelle is going to to seen on the series as well. Apparently, she will be one of the most evil characters on the show come Season 4.

In the first half of the upcoming season, viewers of the show will note that Elsa will assume the role of the villain on the show. Elsa is a character who possesses the power to freeze just about anything that steps in her way. Fans should expect to see a lot of mischief stemming from Elsa in the new season.

Additionally, Kristoff is going to move into Anna's castle, which will not sit well with Anna's beau.

Despite some of the new characters that will be introduced in Season 4, the producers of the show maintained that the series has not entirely changed. Apparently, the fairy tale series will retain many of its elements that are already present in the previous installments.