This is an ongoing joke in the Pokemon series. Jessie and James memorized the motto incorrectly because they aren't the brightest, as explained by Cassidy and Butch in Episode 86.
The real motto as said by Cassidy and Butch:
Cassidy: Prepare for trouble
Butch: And make it double
Cassidy: To infect the world with devastation
Butch: To Blight all peoples in every nation
Cassidy: To denouce the goodness of truth and love
Butch: To extend our wrath to the stars above
Cassidy: Team rocket circling the earth both day and night
A YouTube video of this part is here:
In Japanese, the Team Rocket motto that Musashi and Kojirou (Jessie and James) recite goes like this:
With a translation of (non-localized):
Musashi: If you ask us this or that...
Kojirō: The pity of the world is what responds!
Musashi: To prevent the destruction of the world!
Kojirō: To protect the peace of the world!
Musashi: To stand by the evils of love and truth!
Kojirō: The lovely, charmy villains!
Musashi: The pair from Team Rocket soars through the galaxy!
Kojirō: A white hole, a white tomorrow awaits us!
Nyarth: Something like that!
A YouTube video of Jesse and James performing their original motto can be found here:
Interestingly enough, this joke doesn't seem to happen like it does in the English version. While they do claim to have the correct motto in Episode 86, their motto does not have the same tone the English version does.
Yamato and Kosaburou's (Cassidy and Butch) motto in the Japanese version is as follows:
And the translation:
Yamato: If you ask us this or that...
Kosaburou: We usually don't respond
Both: But we'll make an exception this time and answer!
Yamato: To prevent the destruction of the Earth!
Kosaburou: To protect the peace of the Earth!
Yamato: To stand by evil with love and sincerity!
Kosaburou: The cute, mischievous villains!
Yamato: The pair from Team Rocket soars through the universe!
Kosaburou: Shocking pink, a pink tomorrow awaits us!
Additionally, I wasn't able to understand the joke about the "White Hole", so I've posted that as a question here: Why does Kojirou say "white hole" in the Japanese version of Team Rocket's motto?