These all happen in the Saturday Supercade TV show. To read about other interactions in that show see Saturday Supercade links.
September 17, 1983
TV shows based on both series, called respectively Donkey Kong and Frogger, were produced and aired together in the Saturday Supercade. Additionally, since Donkey Kong aired right after Frogger, the show also featured transition bumpers between the two, showing characters from both series meeting each other. Specifically in this case the clip shows Frogger getting squashed by a car and then Donkey Kong picking him up and inflating him to make him back to normal.
Ruby-Spears was licensed by the games' respective companies (Nintendo and Konami) to produce their cartoons. Once they got the license for both series there was nothing preventing them to make characters from both series appear together.