I have to create a appetizer with these ingredients, lobster, corn on the cob, pineapple juice and can spray cheese. Please help

i would either marinade the lobster in pineapple juice, and/or make a sort of salsa / elote thing with the corn and the pineapple juice

and frankenstein the cheese into a mole sauce

maybe put it all on top of a sope or a tostada

This sounds like a school assignment, or practice for Chopped.
Poach the lobster in the pineapple juice.
Set aside.
Use it in a soup or as a main dish.
For soup, make a chowder using the poached lobster, corn, potato and milk or cream. Top with toast and a layer of the cheese spray (mixed with some grated solid cheese you like or think will go with the other flavors), under the grill a minute or two.
For a main dish, make a polenta with both ground and fresh corn. Serve the poached lobster next to or on it. Ginusb with cheese spray, as before, mixed into a sauce with some grated cheese. Finish with red pepper flakes.