The in-fiction rules of the challenge are in the post below. For convinience let's say no character would decline the challenge as:
1) a kind person would be glad to do a good deed and contribute to charity
2) an evil person would want to use the chance to pass it on someone
3) an indifferent person would go with the flow and do it too
You describe the challanged character's participation (first person perspective or third person perspective are both okay) and include the picture of the character they pass the challenge to. Then the next person does the same using the character you passed it to, and so on.
For convinience I believe it's better to not pass the challenge to more than one character, unless those characters can be considered a group and accept the challenge together (say, siblings... cause I know I'll pass it to Kagamine twins on some point), and when passing to a group, try keppeng the group small (like 2-4 people, don't challenge all of AKB0048 at once or something).
When you accept the challenge as the group, you can still pass the challenge only one time (to a character or another group), not as many times as there are people in the group.
Of course, it would be fun if everyone passed the challenge on a number of characters and it spread just like IBC did, but let's admit we don't have as many people here as youtube does, so it won't work.
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<-- Here's the redhead that started it all, Soryu Asuka Langley.