Prepare brownies as directed on package.
Beat whipped topping mix and 1/2 c milk at high speed with an electric mixer for 5 minutes.
Transfer topping to a seperate bowl and reserve. Do not wash mixer bowl.
Add pudding mix and 1 c milk to bowl and mix on low speed for 2 minutes.
Fold whipped topping into pudding by hand until well mixed. Chill while assembling banana splits.
Place a brownie in th ebottom of a large bowl.
Spread brownie with pineapple topping.
Split a banana in half legthwise and place it next to the brownie on either side.
Place desired amount of banana mousse on top of the brownie.
Top with whipped cream, chocolate topping, nuts, and a cherry.