I haven’t come across paradrop mules in real life – but mules have been used in airborne operations. The Chindits used hundreds of mules during their raids behind Jap lines in WW2. Many were flown in by Dakota and landed at makeshift airstrips, but some went in by glider (with three animals per glider).
A reluctant mule …
http://www.chindits.info/Photos/EA20831.html
More about the Chindits
http://www.chindits.info/