Rainbow Dash loves Tank, and Tank loves her. There is no pony else for him. He would go to Tartarus and back (it might take a minute though) if Rainbow had a problem. The thing is, he's much too slow, even with his helicopter harness, to come to her defense when she needs it-- which is often, what with her being an Element Bearer and all. So when he gets the chance to prove to Rainbow how much he loves her, he takes it-- no matter how annoying Scootaloo is.

Being invited to play at Canterlot Castle for a month is a big opportunity that shouldn't be wasted, no matter how strange others may perceive you to be. So when a young bat pony composer gets the very same offer, in tandem with the re-assimilation of the bat pony tribe into Equestrian Society, she jumps at the chance. But a lot can happen in a month, and she may not be entirely prepared.

(previously entered into an October 2013 Equestria Daily Bat pony Writeoff as a googledoc)