Learn to make a paper mache pineapple, and trick your friends!
Step 1: Gather Your Stuff.
Phonebook/newspaper (whatever is feasible to take into strips)
acrylic paints, spray paint
Step 2: Prep
Take a phonebook or whatever handy and tear strips.
Don't forget to blow up your balloon to however big you want it.
Step 3: Cover Your Balloon
Step 4: Dry Your Paper Mache Balloon.
If you don't have a lot of time, you have two options:
an oven (set at the LOWEST temperature or you risk a fire of epic failure)
Step 5: Paint
After the base-coat drys, (using a real pineapple as inspiration) paint your paper mache!
Step 6: Glue on Leaves
Step 7: Compare
A really good trick is to steal the pineapple tag from the real pineapple and glue it to your fake pineapple.