I understood the joke for the dragon part-- they kept setting up scenarios to make the kids and readers think he's going to blow fire (like pulling out a bag of marshmallows and saying "... You can guess why everyone loves having us at campfires!", or holding up a birthday cake with a bunch of unlit candles), and then he does something else (like making shadow puppets for stories around the campfire or blindfolding kids to hit the piñata at the birthday party), to the frustration of the kids/reader stand-ins-- but I never really got the point of having the firetruck there. None of the proposed scenarios really needed him. I guess the kids were just hoping to see him put out the fire after the dragon lit it? But for cases like the birthday party, if the dragon really did light the candles you wouldn't actually want the firetruck to put those out. Idk, I just feel like it would have made more sense to only have the dragon, and it kind of seems like they were only contriving to have both so they could say it's a sequel to Shark vs Train