A child’s wagon is susceptible to midras impurity (which comes from being sat upon) and it may be handled on Shabbos but it may only be dragged on top of vessels (meaning a surface and not the soil). Rabbi Yehuda said that nothing may be dragged on Shabbos except for a wagon since it presses the dirt down (as opposed to digging a furrow).
One may not catch fish from ponds on yom tov, nor may one feed them, but one may catch wild animals and birds in pens and feed them. Rabban Shimon ben Gamliel says that not all pens are alike. The general rule is that if an animal still requires trapping, it may not be caught on yom tov; if the animal does not require trapping, it is permitted.