Blend both watermelon and pineapple, but separate
Add watermelon cubes in blender with 1/2 of agave, and blend on high until smooth
Add pineapple cubes in blender with 1/2 of agave, and blend on high until smooth
Pour first the watermelon and then the pineapple mixture in the popsicle molds
Freeze for at least 4 hours