In some cases, Cosmo's stupidity rubs off the wrong way on Timmy, and he is usually the one causing Timmy to

Cosmo and Timmy

[1]. Cosmo and Timmy make a bad wish when Wanda is advising against it. Cosmo and Timmy share more of a buddy relationship rather than a father-son relationship. Despite falling for Cosmo's ideas, Timmy is usually well aware of how intelligent Cosmo really is, but if it sounds fun enough Timmy will go with it anyways.
Community content is available under CC-BY-SA unless otherwise noted.