Btw, I don't share stuff712's complaint about the religion in the strip. There is a basic religious notion inherent to this strip's joke, but I'm not bothered.
It is religious because it refers to "hell" as a negative consequence for immoral behavior, which is what the religious concepts of (e.g.) damnation and karma describe. The strip is certainly not specific to any particular religion, but Wally's final remark would lose its punch if rephrased "That's only an issue for people who are already unhappy."