Ubbi Dubbi is part of the Gibberish family of language games, and was popularized by the PBS Kids show 'Zoom'.
Simply place 'ub' before every vowel sound. Remember to put emphasis on every 'ub' that is added, so that it becomes less obvious what you're saying. For example, 'bicycle' becomes 'bubicubycuble', which should be pronounced like 'BUB-eye-SUB-ih-CUBle'.