Ok I'm ticked give me some "GOOD" hints on how to beat giga bowser,mewtwo..

Event Match #51: The Showdown
Character: Whoever you want.
Opponents: Ganondorf, Mewtwo & Giga Bowser!
Arena: Final Destination.
Lives: 3 each.

It's a tough one, no doubt about that, but it's the last one, so keep practicing and keep trying - when you get it done - you'll be completely done and feel great about it lol!

Some tactics...

- Try using Jigglypuff! Why you ask? Because by using her Down+B move, you can KO Giga Bowser at a low percentage if he's near an edge.
- The idea behind Jigglypuff's Rest move is that when you're above an enemy and you use Down+B, if you're directly aligned with that enemy below you, it'll hurt them significantly.

- I've also done this Event with Yoshi - jumping above everyone and getting some height keeps you out of danger for a little while.
- Then use his butt stomp (Down+B) to inflict some damage on hopefully more than one character.
- REPEAT!

- Get rid of Giga first - he's the biggest and the biggest pain!
- You can deal with the other two once Bowser's history.
- Using Items before your opponents is also key!

GOOD LUCK - YOU CAN DO IT =P

You will want to try out all kinds of characters.

Okay first lets get a good laugh. I beat event 51 with Jiggly puff!!! But it was worth it because it was soooo easy! First choose jigglypuff. Then when the match has started attack giga because he has strong attacks. Use jiggly's Down-B attack stay away from the edges, you might fall. After giga is all gone attack Ganondorf. Keep jumping so you can avoid their strong attacks when you come down look out for Ganondorf's Up-B attack. Press R to parry while in the air. Keep using Down-B and then when he's all gone go for Mew-Two. He should be easy if you keep parrying while coming down. Then after he's done YOU HAVE WON!!!

Hope I Helped!!!!!!!

Use Jigglypuff's vB move.
Kill Giga Bowser first.