You know the thing - you get up in the morning and for some inexplicable reason there is a tune going round and round in your head

Sometimes you can figure out why but at other times you can't for the life of you figure out why

example;
this morning I woke up with a popular rugby song going around my noodle - one of those songs designed to be variable in it's object

this morning;
TERry Wogan
TERry Wogan
TERry Wogan is a horse's arse
HE'S the meanest
SUCH a penis
TERry Wogan is a horse's arse

why?

what's the song in your head?