"Knock Knock - Alison" joke

Knock Knock
Who's there!
Alison!
Alison who?
Alison to my radio in the mornings! Knock Knock
Who's there!
Alison!
Alison who?
Alison forgiven, please come home! Knock Knock
Who's there!
Alison!
Alison who?
Alison it's dark outside!