Happily unconcerned; carefree; nonchalant.
(And don't forget to visit the Visual Thesaurus!)
Ok, for fun:
"A scoop of insouciant should remove the odor."
"Insouciant, shminsouciant! Where's my dinner?!?!"
"The new, breezy Insouciant gets 400 miles to the gallon!"
"Failing that, an insouciant should fix 'er right up."
"Ah to be young, and relive the good old days, when the insouciant would not act up."