Considering the lineup of signatures my guess is that the player had battled each of them and asked for their signatures before moving on to the next table
Some combo cards may need to be cut to 2 instead of 3
Appa and the rest of Team Avatar are all Allies, representing how well they work together as a team
The bulk of cards come from the following sets: Power of the Elements, Photon Hypernova, Cyberstorm Access, Duelist Nexus, Age of Overlord, Maze of Memories, Amazing Defenders, Wild Survivors , and Valiant Smashers
I find the hate for it to be very silly and find the archetype incredibly fair, especially compared to what your average Artifact, Lands, Enchantress, Treasure / Food / Clue deck is doing these days
The set adds options to many existing deck styles, ranging from Prince Naveen Ukulele Player slotting into Steelsong decks (an Amber/Steel deck archetype that uses Singer cards to pressure opponents with powerful cards), to Elsa The Fifth Spirit building on the already powerful Ruby/Amethyst control deck, to Madam Mim Elephant adding to the popular bounce decks