Diane McGann is a tall red-headed teenage girl, about the age of Anna's sister, who is constantly riding her black racing bike around town to prepare for bike races. The Pony Pals first meet her when they discover that she is feeding apples to Pam's pony, Lightning, at early hours of the morning, which ended up making Lightning sick. At first she dislikes the Pony Pals - she thinks they are annoying little kids and is skeptical of the information they know about ponies - but eventually she comes to believe them and is worried about Lightning, and by the time the Pony Pals compete in their horse show, she is their friend.

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