Incorrect goof
Incorrectly regarded as a goof, IMDB states:
In the opening credits for the entire series, the type of luggage Felix is carrying changes. When he is indoors (leaving his apartment or arriving at Oscar's) he is carrying a white suitcase. But when he is walking outside he is not carrying the white suitcase.
Whilst this information is indeed true the white suitcase/no white suitcase scenes are not related. The scene with Felix stopping in the street is from Season 1 Episode 5 when he's shunting around between his friends looking for somewhere to stay because Oscar threw him out.
The two scenes with the white suitcase are solely for the credits.
I was walking down the skyway my way...