Purple Potty

The Purple Potty was a time machine created by Melvin Sneedly to retrieve the Combine-O-Tron 2000 so that he could return Mr. Krupp and Melvin Sneedly's brains to their respective bodies.

It is similar to the Tinkle-Time Travelometer and Melvin's later invention, the Gigantic, Glow-In-The-Dark, Robo-Squid, but requires a day in between uses to cool off (otherwise, it runs the risk of malfunctioning). In The Epic Tales of Captain Underpants, Melvin builds the Time Toad 2000 and the The Timetitnca 2000.

Captain Underpants and the Big, Bad Battle of the Bionic Booger Boy - Part 2: The Revenge of the Ridiculous Robo-Boogers
Later after finishing the time machine and getting George Beard and Harold Hutchins into the library, Mr. Melvin explains to George and Harold that they must be careful with the time machine, because if it's used two days in a row (the machine needs to cool off every other day it's used), some unknown bad thing will happen (an oppozo dimensional reality rift will open up if this occurred). He tells them to use the Forgetchamacallit 2000 on anyone that sees them on their journey, so that way nothing bad will happen to the delicate timeline and change the future. George and Harold go back in time two days and retrieve the Combine-O-Tron 2000 after it gets Melvin Sneedly and Captain Underpants back to normal, but before it is smashed (they replace it with a look-alike). This is done thanks to the use of the Forget-chama-call-it on Melvin'sparents.

They go back to the time machine in the library, where Miss Singerbrains steals the Combine-o-tron and the Forget-chama-call-it and drives off to the police station. The boys go back in time and adopt a Quetzalcoatlus and name her, "Crackers", then go back to the moment when Miss Singerbrains stole their stuff, then get their machines back thanks to Crackers. Miss Singerbrains is convinced she is dreaming because pterosaurs don't exist at this time. Harold goes to return Crackers back to her own time period, then they erase Miss Singerbrains's memory and go back to their own

The next day, George, Harold, Sulu and Crackers go into the time machine to send Crackers back home, even though Melvin said something about not using the time machine two days in a row. Harold is hesitant on using it and says that they should let it cool off today, but George assures Harold that nothing bad will happen if they use it two days in a row. The book ends with them starting the time machine, and something bad happening and with George yelling "OH NO!" and Harold yelling "HERE WE GO AGAIN!"

Captain Underpants and the Preposterous Plight of the Purple Potty People
The heroes finally get back to their normal dimension of the multiverse but end up unintentionally bringing Nice Benjamin Krupp, Evil Sulu, Evil George Beard, and Evil Harold Hutchins with them.

Captain Underpants and the Revolting Revenge of the Radioactive Robo-Boxers
They then go to to to the school with a plan to save the two pets by traveling 65 million years ago and leaving them there. However, Benjamin Krupp then notices them and gets mad and furious that the two are running away from him while he is asking them to tell him why they are late to school. It then turns out that he is there with a box of curtains, because they keep on disappearing (due to Captain Underpants using them as capes). When George and Harold reach the library, they lock the door behind them, so Mr. Krupp won't get in. However, Mr. Krupp begins to unlock the door with his keys and barges in after George and Harold who couldn't handle any more problems especially Mr Krupp, they really didn't have the time for him. He then barges in and bangs on the Purple Potty Time Machine demanding that they come out. However, then, Tippy Tinkletrousers then appears again, and is about to freeze Mr. Krupp. However, when they go back in time, Mr. Krupp also goes with them. (As, he was standing too close to the Purple Potty.) Tippy then sends Tiny Tippy Tinkletrousers back in time when George and Harold were going in the Purple Potty and Mr. Krupp soon follows. Tiny Tippy then learns that they're going to the Mesozoic era. He then tells his two selves the news, and the three Tippys go back 65 million years.

Meanwhile, 65 million years ago, George and Harold notice that Mr. Krupp is also there with them hanging on a tree branch calling for help. Harold goes out to grab his hand, but then Tippy kicks the tree. The five are then knocked down and the Purple Potty is then destroyed. George, Harold, and Mr. Krupp are saved by Crackers and Sulu. However, Mr. Krupp does not know this yet.

The Adventures of Ook and Gluk: Kung-Fu Cavemen From the Future
The Purple Potty appears when George and Harold tell the reader how they knew about cavepeople living alongside dinosaurs.