When I first saw this I thought "Why is Dave here, they have no connection". I then listened to the song and It was about a Dad leaving. I then looked at the two of them and suddenly *brain gasp* I realized that they had the same colours and patterns and the facial expressions and then I thought "Dave is Boulderbutt's DAD!". Just LOOK at them. It makes sense!
This is just a theory on @9rainbowtails comic Tales of Perfectheart or ToPH
