William Shatner agreed to be "roasted". I.e. he volunteered to appear in a show where people make fun of him.
The show begins with a clip showing Bill Shatner phoning Leonard to ask him to appear in the show.
 

Leonard Nimoy's answering machine is heard:
"You have reached the home of Leonard Nimoy. Anybody but Bill Shatner please, leave a message." 

"This is, this is William Shatner. Leonard, will you pick up, I wanna invite you to the roast. It's gonna be fantastic. PICK UP THE PHONE, LEONARD!"

"Hello. Hello, Billy, are you in trouble? I saw something on TV about your, your... toast."

"'Roast', you idiot. Turn up the sound in your hearing aid."

"Oh, Bill. Those roasts are terrible, you shouldn't be doing that. They are not for a dignified person like you, a roast is for a pig."

"I'm not dignified. It's a celebration, you know? And I want you to be part of it."

"Why are you doing this? For the food or... What is it?"

"Leonard it's a roast. They get a bunch of comedians nobody's never heard of and celebrities I've never met... "

"Bill..."

"Some trainwreck in a dresses that used to be hot."

"Bill, I 'm not gonna do this."

"And everybody makes fun of me. It's gonna be so much...  fun... I think " (voice trailing off with the realization that it might not)

"Billy, let me tell you something. You know how much I love you. You are like a brother to me"

"I know."

"I consider you a very important person..."

"I am really moved, I really am."

"I really admire what you've done with your career"

"Are you reading this?"

"No, I'm talking to you as a human being, smug! And now listen to me: I am going to do you a big favor: ..."

"Yeah, what's the favor?"

"I will not roast you."

"Oh, Leonard, come on!"

"The answer is no. I, I care about you too much, Bill.
Bill, ...  (Shatner mumbles) ... live long, prosper."

(unnerved) "Ohhh... ... live long and prosper..." 

"I love you, I love your family, give them all my best."

"Well, I'll do that. Thank you , Leonard."

"You're welcome, take care."

"Yeah" Bill presses a button. "You pointed eared pussy eat my barf"

"What ? I'm still on the phone!"

"So, that mean you've reconsidered?"

"Get out of my life!"

Bill's last word is cut off.