London Marathon
Not only is the race the world's biggest in numerical terms, it also raises the most money for charity. Cartoon characters, charging rhinos and Zulu warriors all find their way onto the start line, with thousands of pounds riding on their successful finish.

What does the sentence in italics mean? Cartoon characters, charging rhinos, etc - does it mean that all sorts of people take part in the race?
The London marathon now is a very popular way of getting publicity . So lots of people dress up as comic characters or animals or cartoon characters and take part in the race, not necessarliy to win .
A number of people also take part in the race for charity. How this works ,is that they get the public to promise to donate a sum of money, for every mile that they run in the race. The money goes directly to a designated charity like cancer research or "Save the children" etc etc.
That's what I would say. It means that everyone (or thing) will be there at the race. That there will be a wide variety of participants. That's what I take it to mean.