McDonald had two goals and an assist in the opening period, then capped the scoring with 52 seconds left in the game as the Ducks opened their first playoff series against Vancouver with a 5-1 victory Wednesday night.
"It's pretty exciting," McDonald said of his initial hat trick, playoff or otherwise. "It's just nice to be able to contribute.
"The first game is always tough in the series. I am pretty fortunate to be able to play with such great players."
Jean-Sebastien Giguere finished with 26 saves for the Ducks.
Ryan Getzlaf gave Anaheim a three-goal pad midway through the final period, and McDonald scored on a shot from just right of the crease when the Ducks had a two-man advantage in the closing minute.
With the first multi-goal playoff game of his career, McDonald tied the Ducks' record for most points in a postseason contest and became the second player to have a hat trick. Joffrey Lupul had a four-goal game last May against Colorado in Game 3 of the conference semifinals.
The second game of the series is Friday night in Anaheim before the best-of-seven Western Conference semifinal series shifts to Vancouver for games Sunday and Tuesday.
Luongo faced 31 shots as the Ducks kept the pressure on by crowding in front of the Vancouver goal. He was replaced by Dany Sabourin after Getzlaf's goal. Sabourin faced six shots and gave up McDonald's third goal.
Luongo said the Canucks need to avoid turnovers if they're to beat the Ducks.
"Those are things you can't do in this series. It's going to hurt us every time, especially when [their top line] is on the ice," he said.
"Their first line is fast. We talked about it before and it's nothing that surprises us. We probably learned the lesson the hard way tonight, so we need to bounce back in the next game."
Selanne has been impressed with Luongo, saying, "He's an unbelievable goaltender and we got some good bounces. I watched some games in the other series and he was outstanding.
"We have to make sure he doesn't see all the pucks, otherwise it is going to be too easy for him."
After starting the game relatively slowly and with the Canucks on the attack for the first few minutes, the Ducks quickly shook off the rust. Anaheim hadn't played since wrapping up the opening series against Minnesota last Thursday.
The Canucks didn't really get a day off. They had taken a 3-1 lead in the series against Dallas, but lost the next two before finally concluding the series with a Game 7 win on Monday night. Tuesday was a travel day.
McDonald scored his second goal of the night to give the Ducks a 3-1 lead at 19:11 of the opening period. On a 2-on-1 rush, Selanne skated down the right side, waited for the defender to commit toward him, then slid the puck across to McDonald. The Ducks center beat Luongo with a shot between the pads.
Selanne put Anaheim ahead with a nifty move across the crease. Cutting through the right circle, Selanne took McDonald's pass from behind the goal line, sliced around a defender and beat Luongo with a wrist shot to the stick side.
McDonald's first goal came on a power play during a scramble in front. Luongo blocked Chris Pronger's shot from the blue line, but McDonald controlled the puck. With traffic in front, Luongo had little chance to stop McDonald's shot.
McDonald's and Kunitz's three points in the first period tied a Ducks record for points in a frame in the playoffs. Selanne had a goal and two assists in the second period last year against Colorado. Kunitz notched a career best with three assists and set the team playing record by recording them in one period. ... Along with not getting time off since eliminating Dallas, the Canucks came off a series when they played three overtime games -- a total of 92:15 extra minutes.