The opening begins as Molly tries to say "It's time for Bubble Guppies!" But Gil keeps interrupting by assembling a stage for her. She then manages to say it, but while pretending to be a princess.
Deema is on her way to school when she notices a bunch of actors and a director practicing for the upcoming play 'Three Little Pigs'. She takes a closer look to talk to the director and soon has to leave for school. When she arrives, she tells them what she saw and what happened, and they all begin to think about the important things one needs to put on a play. Gil then sings: Let's Put On a Play
Goby wants to put on a little play, so he goes to the Little Play Store, owned and run by Oona. He finds trouble though trying to pick the right actor for the role. After they successfully make a play. Then Mr. Grouper says it's time for lunch
With the little fish, Gil has made a play. The Little Fish pretend to be the 3 pigs, and a fourth fish pretending to be a wolf. But the fish that should play wolf oinks instead, confusing Gil greatly...
Deema and Goby perform a play with Goby pretending to be a pirate and Deema acting as the Big Bad Wolf. The others compliment her acting, but this makes them curious as to who works in plays. Then Goby sings the dance If You Want to Be an Actor.
Goby and Gil are caveman actors who want to put on a play in the Cave Stage but they find it difficult because Mastodons are blocking it. Soon it gives chase to the two cavemen but they manage to trick the hoard of angry elephant-creatures by pretending to be Mastodons too. After they finally pass the mastodons, they reach the cave stage and they can finally put on a play! About Mastodons...
Gil is still trying to put on a play with the little fishes and he manages to get the wolf one to perform correctly and howl. But when the fishes playing the pigs Moo instead, he just ends up getting very confused, again!
The Guppies go to watch the performance of the watch the play Deema had witnessed earlier and she sees the director from then too! They are then informed that the play can't go on, as the actor who was going to play the big bad wolf is sick. Deema then offers herself to take his place, as everyone thinks she would make a good big bad wolf and the Director allows it! She performs very well, which makes everyone clap for her as the episode comes to an end...
The little fish decide they all want to be The Big Bad Wolf now and they make Gil play the piggy. After he puts on his nose they all decide to give chase!
While the title card reads, "Who's Gonna Play The Big Bad Wolf?", the Little Fish say, "Who's Going To Play The Big Bad Wolf?"