Place muffin pans over ice in a roasting pan to keep the ice cream from melting when broiling the meringue.
Place 12 foil baking cups into muffin pans; sprinkle crushed wafers evenly into cups.
Stir together banana and lemon juice; stir mixture into ice cream. Gently fold in whipped topping. (Do not blend completely.) Freeze for 1 hour or until almost firm.
Spoon ice cream mixture evenly into prepared baking cups. Freeze 8 hours.
Stir together meringue powder, 1/4 cup cold water, and 3 tablespoons sugar. Beat at high speed with an electric mixer 5 minutes. Gradually add remaining 3 tablespoons sugar, beating mixture at high speed for 5 minutes or until stiff peaks form.
Spread 2 tablespoons meringue (working rapidly) over frozen cupcakes in pans, sealing to edge of foil liner. Fill a roasting pan with ice, and place muffin pans over ice.
Broil 5 1/2 inches from heat 2 minutes or until merigue is golden. Remove cupcakes from pans, and serve immediately, or refreeze, if desired.