As you haven't seen it yet, you can't answer this. WHY IN THE HELL WERE THEY IN THIS MOVIE??? Walken barely walks through a scene and Pacino has no more than a cameo. I can't believe they agreed to come anywhere near this monstrosity.

Maybe it was kind of a mutual dare thing.
"Hey, did you get the Gigli script?"
"Yeah. Hey, I dare you to be in it."
"No, way, you do it."
"Come on, I dare ya."
"Only if you do, too."
"Fiiiine."

It's only funny if you picture Walken saying every other line.

That is pretty funny. I can only hope that's why they did it.

There've been people in movies for worse reasons