I play lots of twitch and hell yes he is what the ninjas should be. He pops out of thin air and pentakills your entire team making you think hes the most overpowered champ in the game but he has to be fed for that to happen so follow the advices below to avoid that.
1. No overextending in laningphase. Most opponents make the error of pushing the lane when a twitch is in the game. Lasthitting a creep near your tower gives the same amount of gold than lasthitting them at the opponents tower so why push? Only push a tower when you have at least 1 champion more in your lane than the opposition. If you push solo he will rape you and feed off your sorry ass.
2. If you are not at one of your towers never be alone. Twitch is a great ganker and after the laning phase you should move in a group. Grouping up scares Twitch away since he is so squishy that once stunned hes a guaranteed kill.
3. Focus fire. As soon as Twitch comes out of stealth throw a stun at him. Focus fire him and 2 seconds later its a 4 vs 5 in your favor. He dies so fast he will cry himself to sleep at night from getting pwned so hard. Forget about every other threat on the battlefield, Twitch has to go down first at all costs or your team will get destroyed.
4. If all else fails buy oracles and wards to allow your team to push without being backstabbed, rodent style.