aiding
participating.
All the complex ones that I can think of invlove alterior motives that are more sinister. These simple ones do the tric kbut require additional verbs.
Basically, by the nature of your question, the person is conspiring, but the act in question is a gag, or a ruse, intended for comedic pleasure, hopefully for the victim as well, and does not rely on malintent.
In other works, my bullsh!tting here is done :thumbsup: