"Ren's Toothache" is the eleventh episode of the second season.
Every night, a sleepy Ren is awoken by Stimpy, who keeps his teeth clean, and makes insanely annoying noises in the process. Ren chews out Stimpy and reveals he never brushed his teeth before. Later, Ren finally falls back asleep, but not long before his aching tooth wakes him up. Desperate for an answer to his pain, he turns to Stimpy. Stimpy tells a story about the Tooth Beaver, who gruesomely chews on nerve endings (the tastiest part of the body).
Despite this suffering, Ren still refuses to brush his teeth. His teeth finally begin cracking and decaying. Ren grinds his teeth into dust during the night. He wakes up the next morning with a pile of tooth dust. In the bathroom, he reveals his putrid gums. Ren's mouth has become so disgusting even the Tooth Beaver rejects the idea of biting Ren's nerve ending. Flies emerge from Stimpy's litter box and are so disgusted they leave in frustration. Ren, of course saddened by this, realizes that he should have brushed his teeth. Stimpy, trying to look on the bright side, fails to cheer Ren up, until he tells a story about the Nerve Ending Fairy, who collects nerve endings and leaves you $100 dollar bills, which could allow Ren to buy new teeth.
That night, Ren plucks out his twitchy nerve endings and places them under his pillow. Then, the Nerve Ending Fairy makes a visit. He collects Ren's nerve endings, but realizes he's short on money. So, to make do, he throws a ball of lint under Ren's pillow.
The next morning, an overjoyed Ren is excited to find out what's under his pillow. He is shocked to find a tiny clump of lint. He slowly trudges to the table. He finds a birthday present on the table. Happily unwrapping it, he finds a massive tooth. Ren sticks it into his mouth. He thanks Stimpy, who reveals it was his tooth.
After that, a Log commercial shows up featuring fabulous new versions of Log, including Puppet Show Log, Variable Speed Electro-Log, G.I. Log, Baby Wet Myself Log, Frontier Log, Visible Log, Invisible Log, Log Helmet, Log Underwear, the Log Lunchbox, The Anatomically Correct Log, The Log of Tomorrow and The Super-Deluxe Ultra Log. After showcasing all of the new products from Blammo, the signature theme is played.
- Unlike TV airings, this episode is cut on "The Complete 1st and 2nd Seasons" DVD. The part in the beginning when Ren and Stimpy say goodnight to each other is censored and instead starts the episode with the shot of Ren sleeping. The scene with Stimpy brushing his teeth is also shortened in the DVD release. Stimpy brushes his teeth precisely and very noisy and collects the water he uses to do so in spit jars in the shelf. In the DVD, however, this scene is only the first few seconds. Ren grinds his teeth longer in the TV airings as well. However, the footage is still intact on the Time-Life DVD.
- When Stimpy walks up to the mirror, he has pajamas on. When he walks away from the mirror they disappear.
- When Stimpy hands Ren the mirror at the dining table, his legs disappear.