Complex sentence: While sitting atop his doghouse, putting the finishing touches on his new story, Snoopy receives a letter delivered by Woodstock: he has become Head Beagle ("The Big Bow Wow").
Split into simpler sentences: While sitting atop his doghouse, putting the finishing touches on his new story, Snoopy receives a letter delivered by Woodstock. He learns that he has become Head Beagle ("The Big Bow Wow").