The cover illustration for Chapter 21: Goodbye Yellow Brick Road of The Beach Bears Story.

Drawn for me by the great  kresblain

No, don't worry, Birch is not going to hit Dipper. He is just extremely upset at Dipper's behavior by sneaking off to a party held by a notorious heavy metal rocker. Dipper realized his mistake almost as soon as he got there, but didn't know what to do. Birch came to rescue him, and was understandably upset that Dipper had misbehaved so badly.