It's the artificial flavoring.

Dragged to the circus, Tracy is doing his best to make it a miserable experience, and Tess and Bonnie are doing their best to ignore him and take in all of the sights. The first panel shows us several things. One is that someone decided to bring their bird bath with them for who knows what reason. Another is that not only is there a clown, but there also appears to be a man walking the plank high above the crowd. (We can only hope that he's about to fall into some water or cotton candy or a net or something that won't traumatize all of the little children now begging their parents for those glow wands and stuffed animals that are always sold at the circus.) Moving on to panel two, the trapeze artists have taken to air to amaze and astound with feats of derring-do while Tracy continues to be a wet blanket, choosing to focus on the over-priced popcorn (and probably running through an endless list of things he could be doing instead of being there). Still, as much as I enjoy listening to him complain about each and every little thing, panel three gives me hope that things are about to change. Maybe it's just me, but doesn't it look like that shadowy woman, who I can only assume is the trapeze artist from panel two, is plummeting to her death because the guy in the unitard missed catching her? Better start paying attention, Tracy, things could be about to get a lot more interesting.