By cancelling the action of pulling out the Fishing Rod with an action such as climbing onto Epona or a Boar, or climbing onto vines or ladders, the Fishing Rod actor will be duped and get stuck in Link's hand until you load another area. Continuing to do this will use up space in memory.
By continuously duping Fishing Rods until available memory is low, the loading transition in South Faron will fail, and you can ride Epona out of bounds. Using this, you can enter North Faron with Epona and enter Forest Temple or Sacred Grove early. The most consistent method of achieving this is duping 17-18 rods in the tunnel, loading the Coro area map chunk, pulling out the Fishing Rod one more time, then getting onto Epona and riding to the unloaded Spring area.
By duping Fishing Rods on the vines until memory is critically low, the gate normally blocking the way to Aeralfos will fail to load, allowing you to skip 3 rooms. Duping around 23-24 Fishing Rods, then throwing the boomerang before entering the door is enough to deload the gate. This is slightly faster than going through the rooms normally, but not generally considered worth it in RTA runs.