I think there's no indication as to why his motto would calm him down.
I think I'd reverse the characters (so the computer guy is on the right) and do something like this:
"Oh shits, man! Someone gave us a bad vote on Stripcreator!"
"So?"
"So I'm going to find out who he is and disembowel him!"
"Dude, cool it. Remember your motto, WWBFD?"
"Oh yeah. What Would Barney Fife Do?"
"Right. Now go in the corner and whine ineffectually."
Or something like that. The structure puts the reveal of the meaning of WWBFD right at the beginning of the last panel, and leaves room to explain what that would be. I did Barney Fife because I think it's pretty universal, but you could also do something like:
"Oh yeah. What Would Bill Mumy Do?"
"Right. Now go in the corner and wish them into the cornfield."
Or, if you use the fat character:
"Oh yeah. What Would William Shatner Do?"
"Right. Now go in the kitchen and eat something."
Okay, I'm officially old.
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...Trot and Cap'n Bill were free from anxiety and care. Button-Bright never worried about anything. The Scarecrow, not being able to sleep, looked out of the window and tried to count the stars.