If young Nandi Bushell thought that one day, she might have a cool story to tell about the time that Dave Grohl replied to her on Twitter - well, things just escalated quite significantly.

At this point, the young drummer will be a fully-fledged member of the Foo Fighters by Christmas.

As you may recall, 10-year-old Nandi issued a challenge to the Foo Fighters frontman on Twitter, calling for him to join her in a drum battleGrohl dutifully responded, playing 'Everlong' before challenging Nandi to learn Them Crooked Vultures' 'Dead End Friends'.

The young English girl also aced that song, but now Grohl has come back with something pretty unexpected for Round 2: he's written a theme song for her, enlisting 'The Grohlettes' on backing vocals (i.e. his three daughters) and even producing a video to accompany it.

It's both incredibly sweet and inspiring to see a very famous rock musician be so downright decent to young fans.

As for Nandi's response?