The lighthouse keeper was the disguise of Daphne Blake.
Physical appearance[]
He is an elderly man with gray hair and a beard. He wore a blue captains hat and a large coat over matching pants.
Personality[]
He acted like he didn't know the gang despite calling them to investigate his lighthouse because of a monster, and was also creepy as he was one of three different suspect types Shaggy and Scooby dislike. (Even to his slight confusion)
History[]
Scooby-Doo! 50th Anniversary Giant[]
The disguise was used by Daphne Blake after staging her own disappearance when Velma was explaining about their most common suspects while mystery solving, where she would show up and give everyone a shock and pad out a long conversation until Velma slipped away and wore her disguise.
Daphne and the rest of the gang later revealed to Scooby that they were planning a surprise party for him and that they used the disguises to keep him distracted with a fake mystery while everything was successfully set up.