New York (CNN) -- The tradition that is Macy's Thanksgiving Day Parade has spun off its own tradition -- on Thanksgiving eve, New Yorkers and tourists alike gather on the Upper West Side of New York City to watch their favorite characters come to life in the forms of giant balloons.
On Wednesday, cartoon balloon characters were inflated in a public ceremony before their televised march down Seventh Avenue Thursday morning in the 83rd annual Macy's parade.
The balloon line-up includes returning favorites such as SpongeBob SquarePants, Spiderman and Kermit the Frog. The only balloon newcomer this year is the Pillsbury Doughboy.
Each year, in a tradition that began when Felix the Cat became the first Macy's parade balloon in 1927, all balloons are pre-inflated outside the museum, and are held down with nets and sandbags during the night before the parade.
Every balloon is the product of months of design and testing by the self-named "Balloonatics," who work in the Macy's Parade Studio to turn pencil sketches into ready-for-flight balloons. Sketches become giant clay sculptures the exact size of the parade balloon, and polyurethane fabrics are cut based on the sculptures, then heat-sealed to make the balloon.
Several indoor and outdoor tests are conducted with the balloons by hundreds of balloon handlers, to make sure each balloon can make its flight safely and intact.
The four main giants of Thursday's parade will be Sailor Mickey, Ronald McDonald, Spiderman and the Pillsbury Doughboy. Other notable appearances include a 53.5-foot high Pikachu whose cheeks will emit a rosy glow, and Flying Ace Snoopy which will be making its record 34th appearance in the Thanksgiving Parade.
The 31 balloons that will be featured on Thursday were inflated Wednesday and on public display in a five-block radius around New York's American Museum of Natural History, from 81st to 77th streets between Central Park West and Columbus Avenue.
Macy's workers used hoses to fill each character with helium, section by section, in a careful, time-consuming process. The inflation ceremony attracted a throng of onlookers who were ushered around the netted balloons as they were inflated in preparation for Thursday's parade.