Brawl Breaks Out at Disneyland China, Baby Caught in Crossfire, on Video

Disneyland might be the happiest place on Earth -- but not in this line ... 'cause two couples went from queue to hullaballoo in a wild brawl caught on camera.

Yup, the Happiest Place on Earth turned into chaos real quick -- in this bystander video from Shanghai Disneyland's Crazy Animal City, two dudes vigorously went at it while a woman in bunny ears tried to play peacemaker ... until she popped off at another woman holding a baby.

It's a wild watch -- bunny-ears chick showed zero chill, dramatically shoving the mom, who let out a bloodcurdling scream and collapsed to the ground, clutching her kid, terrified she'd get hit with round two.

Luckily, Bunny Ears bounced back to the brawling bros -- one of 'em hit the ground before others finally stepped in to break it up, and that's where the chaos clip cuts off.

Local reports say it all kicked off over line-cutting -- but things really exploded when one couple tried blocking the other from snapping a pic together. A few words were exchanged ... then all hell broke loose.

No word yet on injuries, but both families could be hit with a lifetime ban for breaking the park's strict no-violence policy.