Dimension High School

One day, on his way to high school, student Junpei picks up an unusual looking rock. Thinking nothing of it, he heads to class. While in the middle of a session, the rock comes to life and transports him and four others to an animated world. To make matters more interesting, the group is introduced to a giant sphinx who is determined to take over the world. Now, to protect their world from invasion, the group must work together as anime characters and real-world humans.

Synopsis from Anime News Network