This one is also fairly easy to understand. Chaos breaks loose while an employee is distracted. One thing that needs explaining is Sue.

Sue is the Field Museum's main dinosaur attraction. She is the world's largest, most complete, best preserved, and most totally awesome Tyrannosaurus rex EVER! She is a she, and named Sue, after the archaelogist who found her, Sue Hendrickson. She is basically the Field Museum's cash cow. The summer she was introduced is affectionately called the "Summer of Sue", but less affectionately talked about by the GR staff, as we saw record numbers, which was good for the museum but chaotic for the employees who deal with guests.

One of the plus sides was that it was so crowded that one could not buy and eat anything from any of the food places in under an hour and a half. Since this would make for impossible lunch breaks, and it was unfeasible to ask every single employee to bring a lunch every day, they set up an employee lunch tent and catered every day (hell, they could afford it with upwards of 20,000 guests coming in on some days). Now, none of this has any relevance to the comic, but it is an interesting and space filling story none-the-less. Also, that drawing is a poor representation of a fellow employee named Adam Sebastian, for those who would like to know if it is based on a real person.