Blue was mad because Red caught his own pony, so he went out and catched his own.
Name change? Click more info to find out why.

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Prolouge (Chapter 1)
The pony is caught (Chapter 2)
St. Patrick's Day (Chapter 3)
Joe (sometime)
Mr. Rodgers (Chapter 4, 5, 6, and 7)
FRIDAY THE 13TH! (Chapter 5)
The Brony Community (Chapter 6)
The Land of Make Believe (Chapter 7)
Nostalgia Critic (chapter 8)
Thomas and the Magic Railroad (Chapter 9)
Tobuscus (Chapter 10)
Enter Trainer Red and Twilight Sparkle (Chapter 11)

Name change? Simple answer, this will go along with the plot of the next chapter in the story. It will be explained why in that chapter.