It sounds like you're referring to a commercial featuring a character named Scotty . However, there is no widely known real diaper brand called "Star Diapers" in major markets (e.g., US, UK, India).
Child psychologists at the time wrote op-eds praising the commercial for showing a “genuinely happy” baby. Competitor commercials often featured overly serene, porcelain-doll babies. Scotty looked like a real toddler: messy, clumsy, and delighted by chaos.
: Founded by Jessica Alba and known for having the " cutest designs " (including star patterns).