Blabber Mouth is an episode of the ALVINNN!!! and The Chipmunks series.
Alvin is convinced that Theodore cursed him so that he can never lie again and can not help himself from blabbing the truth.
During a dark interrogation, Alvin tells Miss Croner a story blaming Theodore for destroying one of her rose bushes leading to Theodore being jetted with water. Theodore confronts Alvin expressing his disdain shortly before Brittany comes to tell them about Miss Miller's surprise birthday party. Dave calls Alvin downstairs to pick up his toys, which he lies claiming they're Simon's. As Alvin prepares for bed, Theodore reinforces the idea that Alvin should tell the truth. During his sleep, Alvin has a nightmare of Theodore and three witches forcing him to drink truth serum. He wakes just as Simon calls him claiming he ate his last cereal bar and Alvin uncontrollably tells the truth. Alvin pleads to Theodore, but Theodore, unaware of Alvin's dream, refuses to remove Alvin's curse as punishment for his lies. Looking for Theodore, Alvin ask Brittany and Jeanette, who want opinions on Miss Miller's surprise party; inadvertently, Alvin ruins the surprise when he honestly answers their neighbor's question. Following a day of upsetting people by telling the truth, Alvin begs Theodore to remove the curse though Theo sells it as a complicated ritual. Not wanting to ruin Dave's meeting with Cecil, Alvin enlists Simon to gag and tie him to a chair so his thoughts aren't heard. During the meeting, a spider lands on Alvin's nose causing him to scream. Ungagged, Alvin accidentally insults the director though Dave is relieved as he felt the same. He apologizes to Miss Miller and Kevin before Theodore lifts the curse in order for Alvin to explain the latest destruction of roses to Miss Croner.
- "Stop Following Me" 
- Series Running Gag: Alvin says the wrong word/phrase - Cecilia B. Cooper instead of Cecil B. Cooper.
- This is the second time in the series Miss Croner is dressed as a witch. The first being Switch Witch.
- The song in this episode was written by AwkwardMarina.