Final answer:
The theme of the passage where Wendell and Grandpa Gamba build a doghouse is cooperation, showcasing the successful outcome of their teamwork.
Step-by-step explanation:
The theme of the passage about Wendell and Grandpa Gamba building a doghouse is cooperation. The passage describes how both individuals contribute their skills and efforts to complete the project successfully. Grandpa brings his building experience, while Wendell contributes artistic ideas and helps by holding the roof. The teamwork between the grandson and grandfather enables them to overcome challenges like attaching the roof, highlighting the effectiveness of working together.