- "Check the wishing well, that's where the secrets are buried"
- ~Grammy Mort to Mort [source]
She is first seen in a flashback in the episode "Fast Food Lemur Nation" when Mort was thinking of what the secret ingredient of the Booty Doodles was. She first appeared real-time in the episode "Out of the Foosa Pen and into the Fire", when Mort ventured into his own mind to find Smart Mort, before having to confront Grammy Mort who wanted to take over his body.
Grammy Mort is part of the Mort kind, a family of mix-breed mouse lemurs who have the ability to consume each others' souls. Grammy Mort has a villainous tendency throughout the series, however not much more is known about her younger days other than what was shown in a few flashbacks from Mort's childhood.
She is married to Grandpa Mort.
Life under Mort's absorption
Grammy Mort's soul was absorbed by Mort more than fifty years ago. Ever since she was trapped in Mort's mind, she had been attempting to take control of Mort's body for her advantage.
When Koto took over the Kingdom of Madagascar, Mort tried to find Smart Mort inside his mind, as he wasn't able to obtain coffee in the Mortverse. However, when he found Smart Mort, he discovered that Smart Mort had been captured by Grammy Mort. Mort tries to tell his grandmother that he's there to take Smart Mort with him to save the Kingdom of Madagascar, but Grammy Mort already knew and was using Smart Mort as bait. Her diabolical plan is to find her way out of Mort's subconsciousness and take control of Mort's body, replacing him and trapping him inside his mind permanently.
Mort then fought Grammy Mort in his mind, which ended with Grammy Mort throwing him down hard onto the ground, creating a large crater beneath. As Grammy dove down from the sky to throw a final punch to defeat him, Mort quickly made a wishing well, causing Grammy Mort to crash into the well and land in the bottom of it, trapped.