Look up there, flying high above the circus ring! No, that's no flying trapeze artist. It's a ... hot air balloon? Does that check out?
Turns out, it actually does. Balloon ascents became a popular part of the British circus tradition in the 19th century. While it might seem pretty strange to a modern audience, remember that the hot air balloon (and flight in general) was a gigantic deal back in the day. It was as bizarre and strange as an elephant calmly taking commands or contortionists bending themselves into nearly inhuman shapes.
And at one of the original British circuses — that would be Philip Astley's in 1840 — the pilot of the balloon decided to bring a leopard onboard to add some interest [source: Victoria and Albert Museum].
Balloon ascents weren't all moonlight and roses, though. Balloonists were under such pressure to perform that they often ascended in unfavorable conditions. In 1871, an acrobat named Professor Torres was performing tricks on a trapeze hanging from a balloon when the balloon exploded. The performer survived the crash, only to drown in another balloon accident later that year [source: Kotar and Gessler].