25: Anime/Manga Synching 1: K-On!: Yui's Foreshadowing

The author writes:
In adapting from one medium to another, events often play out differently. Anime and manga are no exceptions. In the manga of K-On!, the girl calling Yamanaka-sensei was merely a random nameless girl. In adapting the same scene to anime, they made this girl Yui, who in both media would go on to join the club that, in other panels on that page, Ritsu dragged Mio to see Yamanaka to talk about.

Panel source: K-On! vol. 1, p. 5 (no link because it's a licensed manga and thus more up-and-up sites won't carry them; picture is from a scan).

Yui image from a screencap taken from episode 1 of the anime.

Transcript
Yui: Sensei! Yamanaka-sensei: Sorry, someone's calling me.