This clip is from episode 9 and compares the original dub with my edit. Misty's new line "Will you shut your mouth?!" is modified from a line in "The Totodile Duel". Pikachu goes "chu" earlier, the circle-out happens earlier. Brock gets it in the head but good. Owch.
I have made one other modification to this episode, in one place, and might do it elsewhere as well. Some of Pikachu's lines, originally recorded by Ikue Otani, were tracked by Rachael Lillis (the voice of Misty, Jessie and Jigglypuff). Her Pikachu sounds like it's on helium; the voice is more suitable for a Jigglypuff than a Pikachu. Go figure.
This reduces the number of S1 episodes with dubs in need of footage insertion to 2 (18 and 66). 18's just about hopeless because of how much was edited. 66... I don't think it's likely.