Linus' blanket-hating grandmother is the grandmother, of Linus, Lucy, and Rerun van Pelt, and like most adults in the comic strip, has never been seen. As her name implies, she hates Linus' security blanket, and always tries to take it away from him.
The grandmother was first mentioned on March 21, 1960, when Linus told Charlie Brown there are two people in the world against thumb sucking. They are dentists, and interfering grandmothers.
Linus's blanket-hating grandmother is referred to in the TV special, Happiness is a Warm Blanket, Charlie Brown.
While staying for a week at the van Pelt family home, the grandmother demands that Linus stop using his blanket, an act which Linus refuses to do. The whole week, Linus keeps trying to hide his blanket, and ends up successfully hiding it from his grandmother.
The grandmother has featured in the strip's storyline a few more times over the years, and always tries to get Linus to give up his blanket. Linus always dreads her visits. Sometimes, she is successful in stealing Linus' blanket, but he always finds a way to take it back. Linus also uses tricks to prevent his grandmother from finding it, such as using a decoy blanket.
In one storyline, Linus says he will give up his blanket if his grandmother gives up smoking, which she does. Linus has to send a spy (Snoopy) to steal back his blanket.
In another series of strips, Linus' blanket is taken away after he makes fun of his grandmother for drinking thirty-two cups of coffee. After he apologizes, his blanket is returned to him.
Lucy, who also hates Linus's blanket, is on the same team as the grandmother, and always teases Linus when she is coming, making Linus even more worried.
Rerun never has anything to do with his grandmother when she visits and tries to steal Linus's blanket. He always just stays out of the picture. However, Rerun seems to love talking to his grandmother on the phone, and tells her about kindergarten. It is possible that Rerun is talking to his other grandmother, and not the blanket-hating grandmother.