You can either way:
1. Create a variable to work as your random number, and then set the animation to happen based on that variable.
For instance, A = int(random(3)) . If A = 0 play animation "Punching", if A = 1 play animation "Kicking" and so on.
2. Set the name of all animations you want to happen randomly the same. Like, RandomAnimation1, RandomAnimation2, RandomAnimation3... you got my point.
With all the names the same try this:
On overlapping object > Set animation to "RandomAnimation" & intRandom(3)
Hope this helps