The Brain Trust has had several members over its existence. The leader used to be Kyle but in the Battle of the Basement Supply Closet, the Janitor took control. ("My Waste of Time")Margo, Randall, Troy and the Janitor were the original members under the title "Brain Trust." Earlier, Janitor, Margo, Troy and Brent met and had a similar unnamed partnership. ("My Brother, My Keeper") The original Brain Trust disbanded when the Janitor was upset that all he ever got was "tugboats and arson". Janitor says he likes to only have a four-man brain trust, so members come and go always keeping the count at three. This is also a by-law. ("My Soul on Fire, Part 1")Ted, Todd, and Doug Murphy are the current team. Lloyd Slawski also had a try-out (briefly replacing Doug for two meetings) but wasn't accepted after suggesting the Brain Trust rob a house, and for not knowing who Elliot was. ("My Point of No Return") Doug was once again replaced by Sunny because the Janitor thought Doug gave him a dirty look, so he was suspended, even though "he was a good 100 yards away". (Our Meeting with the Braintrust) Sunny was invited because she has a video camera and can therefore record the goings-on of the Brain Trust.
Of all current Brain Trust members, Doug Murphy is the most expendable as he has been replaced twice, but he is shown to be a competent member, giving adequate suggestions to the Janitor for his wedding gift to Elliot. When Lloyd faked his own death to hide from his bookies, Doug was re-instated "permanently", or at least until they found someone else. ("My Soul on Fire, Part 1") In the Bahamas, during the second international Brain Trust meeting, Ira stepped in as the fourth person. ("My Soul on Fire, Part 2") The Brain Trust members all have special pagers that tell them when they are meeting. According to Janitor, the Brain Trust is a "dictatorship masquerading as a democracy". ("My Waste of Time") Janitor also claims that voting is "largely ceremonial" and he has the ultimate power to decide matters. "Brain Trust" is also a registered trademark and the rights to the name is owned by Janitor. ("My Chief Concern")
After Dr. Kelso left Sacred Heart Hospital, Janitor claimed Kelso's office for the Brain Trust, named the "Brain House", and restored Ted's confidence. When Janitor reminded the members of the Brain Trust that Tuesday night was their night to clean the hospital, Ted got upset and broke with Doug into his own "Brain Bunch". Janitor didn't want to be stuck with Todd so he and Ted swapped Doug for Todd. Janitor realized that his Brain Trust was nothing with only 2 members, so he made some concessions and allowed Ted to have a night to play cards instead of cleaning the hospital. ("My Waste of Time")