McMillan’s most successful book is Why do dogs sniff bottoms?, illustrated by Ross Kinnaird(Reed, 2002). This was her first work written in verse.

Why do dogs sniff bottoms? won the Children's Choice Award at the 2003 New Zealand Post Book Awards for Children and Young Adults , and was awarded New Zealand Booksellers Gold in 2005. This delightfully funny account is brought to life through witty verse and hilarious illustrations which perfectly capture the rhythm of the verse.

The answer to one of life’s mysteries is now revealed – why exactly do dogs sniff bottoms? This delightfully funny account is brought to life through witty verse and hilarious illustrations which perfectly capture the rhythm of the verse.