Bring a large pot of salted water to a rolling boil. Add the small shell pasta and cook according to package directions, usually about 7-9 minutes, until al dente. Drain the pasta in a colander and rinse under cold water until fully cooled.

In a large mixing bowl, combine the drained whole kernel corn, drained Rotel, and chopped green onions. Mix gently to incorporate all the ingredients.

In a medium bowl, whisk together the mayonnaise and sour cream until smooth and creamy, ensuring there are no lumps.

Pour the creamy dressing into the bowl with the corn mixture, stirring gently to coat all the vegetables evenly.

Carefully fold in the shredded cheddar cheese, followed by the cooled shell pasta, mixing gently.

Cover the salad with plastic wrap and refrigerate for at least 1-2 hours.

Once chilled, give the salad a gentle stir, transfer to a serving bowl, and garnish as desired.