This quote means that comedy involves taking everyday facts and events and adding a humorous twist. This can be in the form of exaggeration, irony, sarcasm, or other types of humorous devices. For example, someone might take an everyday event like going to the grocery store and add a funny element like pointing out how absurdly expensive produce is or how strange the other shoppers are. This could be considered adding a “curlicue at the end” of a truth.