What is the name of the cartoon with the Lightning Dog? - briefly
The cartoon you are referring to is called "Sky Whale".
What is the name of the cartoon with the Lightning Dog? - in detail
The cartoon you are referring to is likely "Courage the Cowardly Dog." This animated series, created by John R. Dilworth, features a unique and memorable character named Lightning. Lightning is a pink dog with a lightning bolt on his head, which gives him the ability to generate electrical energy. He is one of the main characters in the show, known for his mischievous behavior and occasional helpfulness to Courage, the titular cowardly dog. The series premiered on Cartoon Network in 1999 and ran for four seasons, gaining a dedicated following among fans of animated comedy.