People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zheng Huansong)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zheng Huansong)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zheng Huansong)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zhang Cheng)

People attend the Balloon's Day Parade of the 2019 Brussels Comic Strip Festival in Brussels, Belgium, Sept. 15, 2019. The Balloon's Day Parade is a traditional show during each year's comic festival. (Xinhua/Zheng Huansong)