Boss Delguapo (a parody name of Hoss Delgado) is the worlds greatest Dragon Slayer (at least, that what he says). And because of this, Grim takes Billy and Mandy to him so Billy can train to be a Dragon Slayer and become a hero. After Boss trains Billy to kill the dragon, Billy refuses because of the times Billy and the dragon shared together, then Boss goes to kill the dragon which makes Billy shoot Boss with Grim's scythe causing Boss to travel forward in time, to the present (in Endsville) were he works for a Chinese restaurant advertising their sales on egg roles, ironically he does this in a dragon suit.