China Anne McClain was going to audition for Rocky Blue but she was too sick to make it to auditions, leaving Rocky and Cece's ages at the start of the series to be changed from 12 to 13. She'd later star as a Main Cast Member in A.N.T. Farm (2011) 1 year later, a show that Zendaya (Rocky) made a guest appearance on in one of the episodes.
Rocky Blue is Zendaya's Very First Role on Disney Channel. Later she'd star in 2 Disney Channel Original Movies (Frenemies (2012) and Zapped (2014)), as well the Main Character of Another Show that Premiered 14 Months after Shake It Up! (2010) aired it's Final Episode in November 2013, K.C. Undercover (2015).
For Unknown Reasons, despite Tinka appearing fairly frequently in the show alongside her Twin Brother Gunther, and appearing more in the show than he did, Caroline Sunshine was not shown in the Intro for Season 1, but would later be added to the Intros of the Other 2 Seasons. A similar thing happened with Corey Fogelmanis in Girl Meets World (2014) 4 years later.
Though not part of the cast, Selena Gomez from Wizards of Waverly Place (2007) sang the Show's Theme Song. In Season 3 it was cut to only less than 30 seconds, shortening the intro and removing Kenton Duty (Gunther) due to him leaving the cast, reducing the amount of Main Cast Members from 7 to 6.