tl;dr - find and use AIML files
There is an open-source chat-box project called A.L.I.C.E.
Link to Demo
A.L.I.C.E. uses the AIML format
AIML (Artificial Intelligence Markup Language) is an XML-compliant language that's easy to learn, and makes it possible for you to begin customizing an Alicebot or creating one from scratch within minutes.
The most important units of AIML are:
aiml: the tag that begins and ends an AIML document
category: the tag that marks a "unit of knowledge" in an Alicebot's knowledge base
pattern: used to contain a simple pattern that matches what a user may
say or type to an Alicebot
template: contains the response to a user input
<pattern>WHAT ARE YOU</pattern>
I am the latest result in artificial intelligence,
which can reproduce the capabilities of the human brain
with greater speed and accuracy.
Here are links to AIML datasets : http://www.alicebot.org/downloads/sets.html
You can also probably search Github for AIML formats: https://github.com/search?q=aiml