They serve their purposes in The Plan.
I was just writing up Justin's evaluation for the Big Shat (Mr. Shatner to you) and it's nice to know that his irritation factor for your age group is effective. As for Mr. Carey, well, his usefulness is almost at an end, which is why he's not being positioned in better films. We've already got Mr. Cera and Mr. Rogen ready to replace him.
I'm also Avril Lavigne's handler, by the way. Is her tough-but-cutesy attitude getting to you yet? Do we need to make her more vapid?
Muzzy, aka "Big M", Ministry for Canadian Singer Qualification for U.S. Entertainment Enterprises (MCSQUEE)