What kind of bot? There are at least tree:
What you need to be done will influence how you build your bot.
You can read more there: http://en.wikipedia.org/wiki/Wikipedia:Bots
That's hard to make because you'd have to either hardcode phrases so that even if someone says hi instead of hello, if hi isn't harcoded, there will be no response. The other way, which is a complete pain to do, is creating a neural network which understands the questions being asked for responses. Not impossible, but very hard.
What do you think?