My friend always had a suspicion that Roger from Doug had his laugh recorded once and re-used over and over. Turns out he was right
You Nostalgia You Lose: Every Roger Klotz Cackle From Doug | Geekosystem
That is pretty nostalgic. I used to watch that show when I was a kid and I too remembered his evil annoying laugh and how it sounded the same every time. I didn't suspect it was copied over and over again, though. I just thought the voice actor had the skill to do it over and over and over again.