Plankton tries hard to get Mister Mussel to return a friendly greeting, but when Mussel finally opens his mouth the results are unfortunate for Plankton.

"Cangrejito es un cangrejo muy gruñón. Plancton quiere alegrar a Cangrejito. Plancton le cuento un chiste a Cangrejito. Plancton le hornea un pastel a Cangrejito. ¿Padrá Cangrejito sonreír alguna vez?"--Back cover. Crabby, far from being a happy crab, is quite crabby, so when pushy Plankton, who is always trying to cheer up fellow marine creatures, bakes Crabby a cake, even this might not be enough to make him smile.

Crabby is a very grumpy crab, so Plankton tries to find a game that will cheer Crabby up, but Crabby does not want to play Simon says or hide-and-seek---will a game of tag be more to Crabby's taste?

It is late and Crabby just wants to sleep, but Plankton keeps Crabby awake with questions and chatter--until a request for a bedtime story takes an unexpected turn. "¡Es hora de irse a la cama! Cangrejito quiere ir a dormir, pero Plancton quiere darse un baño y que le lean un cuento. ¿Podrá dormir Cangrejito?"--Back cover.

Plankton gets the idea to play school with Crabby as the student, but Crabby is more interested in recess and uses wordplay to confuse Plankton and get his way.