Belle, the second sibling to be introduced, debuted on June 28, 1976. "I found my sister Belle ... and what a reunion we're having!" Charlie Brown reads from Snoopy's letter in a later strip.

Belle, the second sibling to be introduced, debuted on June 28, 1976. "I found my sister Belle ... and what a reunion we're having!" Charlie Brown reads from Snoopy's letter in a later strip.

Belle, the second sibling to be introduced, debuted on June 28, 1976. "I found my sister Belle ... and what a reunion we're having!" Charlie Brown reads from Snoopy's letter in a later strip.

Belle, the second sibling to be introduced, debuted on June 28, 1976. "I found my sister Belle ... and what a reunion we're having!" Charlie Brown reads from Snoopy's letter in a later strip.