This is a version that I use (though not from Disney). If you try it, let me know if it's like the one you had at Boardwalk Inn.
Lemon Drop Martini
2 oz vodka
1 oz triple sec
2 oz margarita mix
1 tsp sugar
1 tbsp lemon juice
Place the sugar and lemon juice in a cocktail shaker. Swirl the shaker around so that both ingredients are mixed thoroughly. Add ice cubes. Add the vodka, triple sec and margarita mix, and shake well. Strain into a cocktail glass. Add rimmers to make the drink look nice, if you have them.