From Homestar Runner Wiki
Pasta Salad is the mysterious yet delicious taste sensation enjoyed by Strong Mad in the email "old comics". According to Strong Bad, the pasta salad arrived in his brother's underdrawer drawer due to the "Who Put Pasta Salad in Strong Mad's Underdrawer Drawer Scare of '04".
Although described by his brother as a "scare", the existence of the pasta salad does not prevent Strong Mad from wolfing down spoonfuls of it and bellowing "IT TASTES SO GOOD!"
An overly hyperactive Strong Sad also briefly mentions pasta salad in the email "caffeine".