Heat oven to 400° F.
Arrange the potatoes, sausage, corn, and shrimp on the sheet pan in a layer. Mix them up.
In a cup, mix together the melted butter and garlic. Pour it over the sheet pan ingredients and mix together.
Sprinkle the Old Bay and the Cajun/Creole seasoning over the sheet pan ingredients and mix together.
Squirt some of the lemons over the sheet pan ingredients. Then arrange the lemon wedges on the sheet pan.
Bake in a 400° oven for 13 to 20 minutes, or until the shrimp is no longer translucent, and the potatoes are tender when pierced with a fork.
You can season with more of the seasonings as desired.
Garnish with fresh parsley.
Serve directly from the sheet pan.