Note: This Mystery is based on the following info:
Iggy has a yellow wand, Morton has a red wand, Lemmy has a green wand, Ludwig has a gray wand, Roy has a black wand, Wendy has a purple wand, Larry has an orange wand, Susan has a pink wand, and Bowser Jr. has his paintbrush. These are their weapons. This combination will be used in all of my Mysteries.
I consider Junior and Susan to be Koopalings, and Susan is younger than Iggy but older than Wendy.

One day, the Koopalings other than Ludwig are in Ludwig’s room. Susan is trying to offer Piranha Plants to Larry, Roy is beating up Iggy, Iggy is considering contact lens for the first time, Larry is rejecting the Piranha Plants, Morton’s blabbing about wedding cake. Wendy’s sneaking up on Susan to steal her jewels, Lemmy’s practicing a trick, and Bowser Jr’s doing random stuff. Bowser comes in.

Bowser: All right kids, if no one falls asleep during Ludwig’s presentation, I’ll buy some iced cream.

Ludwig (behind Bowser): Don’t you mean ice cream?

Bowser: I SAID ICED CREAM! Bye!

He leaves.

Ludwig: Now, you shall see my vonderful machine, the Energy Splicer!

Bowser Jr: What does it do?

Ludwig: It divides your energy and recombines its deoxyribunocleic acids to make it stronger.

Wendy: Deoxys what?

Iggy: He means DNA.

Ludwig: Right. Now, it is attached to a teleporter so vee can teleport to Peach and destroy her vunce and for all.

Bowser Jr: What is this, some contest?

Ludwig: Yes. Vee shall compete to kill Peach. Vee shall go on a killing spree until the killer returns here.

Susan raises her hand.

Ludwig: Yes?

Susan: First, what’s iced cream, and second, can we kill each other?

Ludwig: I don’t know, and yes, since vee are competing to kill Peach, vee may kill each other.

Koopalings: KOOL!

They enter the splicer with their weapons. But a cloaked figure appears and sets the splicer on red-hot fire as the last few Koopalings are being teleported.

Figure: The only one who will kill Peach shall be me! And by me, I mean no one!

The figure leaves and hammers some guards.

At Peach Gardens, one of the last Koopalings to be teleported becomes the first to make a move as he silently sneaks towards Peach, but the burnt splicer messed up this Koopaling’s DNA, and it ends up getting killed. His wand falls to the floor.

Another Koopaling tries to get to Peach but is throughly beaten up by another Koopaling. The first Koopaling, for once, doesn’t say anything as the two of them die too. Then the youngest Koopaling comes by.

Koopaling: I’m sure I’ll do it!

It is then killed by the fifth oldest Koopaling, who then dies from bad DNA like the first had. Then the Koopaling that said DNA also dies.

The Koopaling that I didn’t mention doing anything burns the wands on the floor. It then dies.

A bald Koopaling finally kills Peach, but is killed by the last Koopaling remaining. It takes the remaining wands and hides them in the castle.