dear
Explanation
The Joke
The comic shows a man kneeling in prayer, hands clasped together, trying to begin his prayer with "Dear..." but he keeps stammering: "Dear... Dear... Dammit I just can't do it without feeling stupid!" The caption below explains: "In order to limit the number of incoming prayers, God changes his name to Dave."
The premise is that God has strategically changed his name so that people cannot comfortably address their prayers. Prayers traditionally begin with "Dear God" or "Dear Lord," but nobody can bring themselves to sincerely say "Dear Dave" in a solemn, prayerful tone. The format sounds too casual, too much like writing a letter to a coworker, and so the man feels ridiculous and cannot complete his prayer.
The Humor
The joke works because it treats God as someone dealing with a practical problem -- too many incoming prayers -- and solving it with a clever bureaucratic hack rather than divine power. Changing his name to something mundane like "Dave" exploits the awkwardness of addressing something sacred with informal language. The humor also comes from the man's genuine frustration: he clearly wants to pray, he has something important to say, but the sheer absurdity of saying "Dear Dave" to the Almighty is an insurmountable psychological barrier. It is a simple, elegant joke about the gap between the sacred and the mundane.