In one of the very first shots of the film, there’s a rainbow over Oz. This is perhaps the most obvious Easter egg and a direct callback to The Wizard of Oz and “Somewhere Over the Rainbow”—it immediately lets audiences know the stories are intertwined.

All the main characters from The Wizard of Oz make a cameo in Wicked, as the camera pans over Oz right before “No One Mourns the Wicked.” This is a clear indication of what’s coming in Part 2, which is Elphaba and Glinda’s POV of the events of The Wizard of Oz.