Alyson Hannigan and hubby Alexis Denisof picked up some party supplies in Santa Monica Friday ... in the form of some HUGE, brightly-colored balloons.

Little Satyana Marie's third birthday isn't until the end of the month, but perhaps the family was getting a jump on the big day? Or maybe the smiley-faced sunshines and rainbow-colored butterflies were just an accessory to brighten their day!

The How I Met Your Mother star announced her second pregnancy back in December so she could be due around mid-May, assuming she announced at the beginning of her second trimester. In fact, her character on the show is due in May, so perhaps producers are writing the show in real-time!