Example 1
He always does some crazy things and when he does, the girls freak out.
Can it be rewritten to the following without altering the original meaning,
Example 2
He always does some crazy things and the girls freak out.
Example 3
He always does some crazy things and the girls will freak out.
In example 1 it is clear that the girls are freaking out because of the crazy things he does.
In examples 2 and 3, the causal relationship is less clear. If within the context, there is another potential cause for the girls to freak out (other than the crazy things he does), it would be possible to interpret the sentence as a list of different reactions to a different stimulus (established by previous context).
For example, if the preceding sentence said "All the students have different reactions when there are thunderstorms outside." then we would not necessarily think that the crazy things he does cause the girls to freak out, they could be freaking out due to the thunderstorms.
In coordinated constructions like this:
A {does | will do something} and B {does | will do something}.
the coordination with and is often intended to express a cause-and-effect relationship and in conversation it will usually be understood in that way, but a causal relationship is not entailed by coordination.
So feel free to say it that way in casual conversation; but you should be more explicit and not rely on "and" if you want to make sure your audience understands there is a causal connection.
