My oldest loved Dora. I remember one night when she was around 5 months old and up with a fever and nothing was making her happy, Dora it was. We watched Dora however long she wanted that night because it was the only thing in that moment that made her happy.
My youngest loved My friends Tigger and Pooh
My nephew loved the Wiggles
My niece loved Backyardigans
All of them as infants used to love the opening song and dance to their favorite show just as you have stated about your son.
All of these kids are grown, the youngest being mine at 3 years old, and all of them MUCH prefer to be outside than watching TV. I wouldn't worry so much if I were you.