What is the order of Waterfront Bouncer's ability + Basking Rootwalla + Intruder Alarm on the stack?
This is the order of events: 


You announce that you wish to activate the Bouncer's ability. As part of activating the ability, you pay the costs and choose the target (which has to be on the battlefield). The Rootwalla goes from your hand into exile when you discard it, the Bouncer is tapped, and you put the ability on the stack
The madness ability triggers, and you put that on the stack on top of the Bouncer's ability
Each player gets the opportunity to play spells and activate abilities (a "priority wave" happens; I'll go ahead and assume that no additional spells and abilities are played, but I'll indicate where players have the opportunity)
The madness triggered ability resolves, during which you get to choose whether to play the Rootwalla or put it into your graveyard. I'll assume you choose to play it. This makes the Rootwalla a spell on the stack, on top of the Bouncer's ability
New priority wave
The Rootwalla resolves, and becomes a creature on your battlefield
The intruder alarm's triggered ability triggers, and is put on the stack on top of the Bouncer's ability
Priority wave
Intruder alarm resolves, untapping all creatures
Priority wave
The Bouncer's ability resolves, returning the originally targeted creature to its owner's hand