It is a song from the 1964 musical film Mary Poppins.
The correct spelling is supercalifragilisticexpialidocious.
(see related question)
nonintervention
Carats.
bandoleersbusinessesbandicootsbuttoneersballoonersBraziliansbattalionsboyfriendsbellyachesbiologistsbeautifiesbadragglesbesmirchesbotanicalsbillboardsbubblegumsBostoniansbenchpressbrassieres
Daffodill
Brittany
CandyCarryCrazyCassyCatty
diligent
carilium
One example of a long word that starts with "s" and ends with "r" is "supercomputer."
It starts September 15th ends October 15th.
Kayla. Karla too.
Chicken