How can I get to the cannon?

Hint 1 of 5:

Maybe you could just ask the pirate guarding it politely?

Hint 2 of 5:

Well, that doesn't quite work, but talking should.

Hint 3 of 5:

Keep talking to the pirate, and you'll eventually realize you know him.

Hint 4 of 5:

It's Wally, from the previous games in the series.  And he was a good guy
then!

Hint 5 of 5:

Just keep badgering him and telling him what a failure he is as a pirate. 
Eventually, he will agree and start to cry.