Appearing in a single episode of the Venture Bros called Momma's Boys, the Momma's Boys were a short-lived cult of Dunwitch Asylum inmates (and at least one guard) who served Myra Brandish. They knew her as "Mother", for she had beguiled them she was their mother, or more perhaps a maternal, almost god-like figure who took care of and didn't judge her "children." (She may not have been using them as an intentional charlatan.)
The cult revered Myra perhaps not only as a normal mother but also a maternal spiritual figure. (She is seen being carried on a palanquin dressed in a manner perhaps similar to some depictions of the Virgin Mary.) At least two of her followers bear "Mother" heart tattoos on their chests.
Myra Brandish has a long history of escapes from previous incarcerations in insane asylums. Due to Doctor Thaddeus Venture's manipulations, she came to see Dean Venture and Hank Venture as her biological children, though she recognizes she never gave birth to them. Apparently at some point she began building a power base of followers while held in the Dunwitch Asylum for the Criminally Obsessive. By the time of the fifth season episode Momma's Boys, she has gathered a large number of cultists behind her.
In The Episode Momma's Boys
In this episode, Hank Venture and Gary Fischer infiltrate Dunwitch as committed insane supervillains in the hopes of finding Teddy Talk-To-Me. Inside the asylum, they locate him among the other inmates. When Hank recognizes him and calls him by name, Teddy tells Hank he must be mistaken. Radical Left rips open his shirt, revealing a a heart tattoo with "Mother" written on it. He tells Gary and Hank that all the inmates are Momma's Boys and then asks Gary if he's Momma's Boy. Gary says he loves his mother, to which Teddy replies that today's his lucky day, for it's Mother's Day. They will all become a happy family. Before Hank can elicit help from Teddy, Cuckoo Clocker begins punching the asylum guards and thereby starts a riot.
Meanwhile, Dean visits Myra in the asylum and meets her in a meeting room. One of the asylum guards tells Dean Myra loves him, they all love him. After Myra comes in with another guard, Myra and Dean embrace to the objection of the guard she came with. The initial guard knocks out the new guard with the butt of his gun and reveals his nature as one of Momma's Boys. Using deception and guile, Myra ferrets Dean away further into the asylum.
Back with the inmates, the guards have been subdued with the prisoners freed in the aftermath of the riot. Myra makes a grand entrance carried on a palanquin along with Dean, who is wrapped up head to toe. Not noticing Hank, Myra asks Big Time if he can take her back to the time when Dean was born. Myra also asks Maybe Man if he can put Dean into her womb so she can have her inside him and give birth like she was supposed to.
Tipped off by Myra's desire to have Dean put into her womb, Hank figures out that she's not their mother. She calls Myra out on her lies, and Gary says she's not his mother either. Together they convince the other inmates that Myra helped build up the metaphorical and literal walls around them and to "tear down the walls". The inmates rebel, throwing off her psychological grip. Giant Indian throws a drinking fountain through a window, and the inmates begin fleeing the asylum. Myra tries to calm down her followers, but she fails and suffers a psychological breakdown.