Episode 83: Shampoo's Red Thread of Dread!

Subtitled
Dubbed
Shampoo obtains the "Red Thread of Fate," which can make anyone fall head-over-heels in love with the user. She of course wastes no time tying it to Ranma's pinky. Ranma immediately starts acting weird and can't keep himself away from Shampoo.
TV-14

Available on DVD / Blu-ray