From taking a jab at Rosie O'Donnell to consoling Sen. Rand Paul on a difficult night, here are Donald Trump's memorable lines from his first GOP presidential debate. (Fox News Channel)

Business mogul Donald Trump said in the days leading to Thursday night's GOP presidential debate that he would prefer to play nice. “You watch,” he said earlier this week. “I am going to keep it on a high level. I have a lot of respect for them.”

We learned Thursday night night that distinguishing between the way Trump speaks about and to people he respects, and the way he speaks about people he doesn't, is a remarkably difficult exercise.

Herein: A list of the people Donald Trump insulted during the debate:

  • Kentucky Sen. Rand Paul: “Well, I've given him plenty of money.”
  • Paul again: “I don't think you heard me. You're having a hard time tonight.”
  • Rosie O’Donnell: Megyn Kelly asked why Trump has called women "fat pigs, dogs, slobs, and disgusting animals" on social media. “Only Rosie O'Donnell,” Trump responded.
  • Reporters: “[T]hey're a very dishonest lot, generally speaking, in the world of politics.”
  • America’s leaders: “The Mexican government is much smarter, much sharper, much more cunning. And they send the bad ones over because they don't want to pay for them. They don't want to take care of them. Why should they when the stupid leaders of the United States will do it for them? And that's what is happening whether you like it or not.”
  • Other people in Washington too: “We have people in Washington that don't know what they're doing.”
  • Hillary Clinton: “Well, I'll tell you what, with Hillary Clinton, I said be at my wedding and she came to my wedding. You know why? She didn't have a choice because I gave. I gave to a foundation that, frankly, that foundation is supposed to do good. I didn't know her money would be used on private jets going all over the world.”
  • Lenders: “Let me just tell you about the lenders. First of all, these lenders aren't babies. These are total killers. These are not the nice, sweet little people that you think, OK?”
  • Fox anchor Chris Wallace: “You know, I mean you're living in a world of the make-believe, Chris, you want to know the truth.”
  • former president George W. Bush: “The last number of months of [Jeb Bush's] brother's administration were a catastrophe. And unfortunately, those few months gave us President Obama. And you can't be happy about that.”
  • President Obama: “I would be so different from what you have right now. Like, the polar opposite. We have a president who doesn't have a clue. I would say he's incompetent, but I don't want to do that because that's not nice.”
  • The United States, as a whole: “Our country is in serious trouble. We don’t win anymore… We can’t beat Mexico, at the border or in trade. We can’t do anything right.”

Immediately following the debate, Trump began insulting moderator Megyn Kelly.

"The questions to me were not nice. I didn't think they were appropriate. And I thought Megyn behaved very badly, personally," he told reporters.

Then he lobbed more insults on Twitter.

He insulted her Fox debate co-moderators.

But with the morning, Trump ventured into kinder, gentler territory: on Friday, he complimented each his top-tier GOP rivals during an appearance on MSNBC’s “Morning Joe.”

  • Marco Rubio: "Well, I thought Marco was terrific. I supported him in the past. I don't know that I've ever met him. I don't think I've met him. Very good guy."
  • Scott Walker: "Walker, good guy."
  • Ben Carson: "Carson, terrific guy. I've known him before."
  • Jeb Bush: "I got to know Jeb Bush really for the first time. He was a terrific guy. Really a nice guy."

Trump is next scheduled to respectfully address his rivals onstage when CNN hosts the Republican debate in September at the Ronald Reagan Presidential Library in Simi Valley, Calif.