I mean, let's face it... this IS a sci-fi show (as much as it pains me to admit that, it's true) and as with all sci-fi shows, there HAS to be the prerequisite time travel episode. I wonder how the writers would deal with it? Perhaps it would go something like this:
Leela: Dammit! We missed the landing window! Now countless millions of Zifarians will die because we couldn't get our delivery of water on time! A horrible plague and all they needed was a little H20.
Fry: That's terrible! Isn't there anything we can do?
Bender: We could enter their atmosphere, open a window and urinate or spit on some of them. That'd help, wouldn't it?
Fry: Heheh. Finally a comeback to the line "It's better to be pissed off than pissed on."
Leela: Nice idea, Bender, if a little twisted. No. We'll just go back in time and deliver it then.
Fry: WOW! You mean we can time travel? COOL!
Leela: Bender, you're a robot. Make the calculations to send us back two days in time. That way we can deliver the water antidote before we needed to and they have enough time to administer it.
Fry: But won't that cause, like, a paradox or something? It could rip a hole in the time/space continuum. I think.
Leela: Hey, I don't write the script, I just do what I'm told. Do it, Bender.
Bender (warily): Okaaaay. (works madly on his computer for a few seconds) Done!
Leela: Good Did you send it to my navigation computer?
Bender: Yup.
Amy (from her station in the back of the ship): Hey! What's with all the numbers???
Bender: Ooops. Sorry. Now ya got it, Leela.
Leela: Okay, I see it. Hold on to your girders, everybody!
Bender: THAT'S NOT FUNNY!!
The ship seems to shimmer out of normal space for a few seconds and then it reappears.
Leela: Okay! We're though. How far back did we come?
Bender (check his computer): Ahhh... two minutes.
Leela: WHAT?!?!?
Bender: Hey, what'd you expect? I'm an alcoholic robot, not an engineer.
Well... it COULD happen like that. =D