Behind a cover so bursting with characters and joy that I think it may be my single favourite piece of Adventure Time art, possibly my favourite single issue of the comic so far. Beginning in prehistory (turns out Ryan North has a gift for these...dinosaur comics?), it moves through Marceline and Bubblegum's relationship to 'present' Ooo and beyond. Guest artists including Jess Fink help keep the eras distinct, but there's one thematic thread (or rather, braid of threads) running through them all, and it's beautiful.
The rest of the volume is taken up with an exploration of mind/body duality. This can be quite a dry topic in many media, but because comics are awesome, they tend to handle it pretty well. Grant Morrison gave us a robot snogging an ape, then exploding; North and Rugg have ghost teamwork, Princess BMO and a starter dungeon for babies. Cartesian!