"A retired Maori activist who has become an MP working with a hard left unionist and let's just throw in a wealthy German millionaire right-winger, they could form a political party," said.
"That's the sort of wacky thing that could happen between now and September 20.
"If Laila Harre, Hone Harawira, Pam Corkery, Kim Dotcom, Russel Norman, Metiria Turei, David Cunliffe, Matt McCarten, and John Minto are the answer, can we please have another look at the question?"
Mr Joyce announced that the party's campaign slogan would be "working for New Zealand."
He said National would be setting up a social media hub called "Team Key" that would collect National's social media traffic as well as policies and announcements during the campaign.
He also announced that the campaign would be setting numerical targets in each electorate for the party vote, not a percentage target.
The highest targets would be for 25,000 party votes, graduating down to 20,000, 15,000 and 2000 to 10,000.
"It is not enough to get a certain percentage of whoever turns out," Mr Joyce said. "It's important to get as many as possible people to turn out."
The percentage of votes in the electorate was not as important as the number of people who actually voted.
Mr Joyce urged delegates to take no comfort from recent polls showing National with a strong lead over other parties.
He said comparing the average of the main opinion polls now with 84 days out from the last election, National is now running about two points behind.