These are in no particular order. I think somebody else may have compiled a list like this, but this is mine with my own spin on it. :P.
1. Kafka: Back when I was a kid I didn’t get the reference of the name of the character. I just thought it was a silly talking cockroach. I wish the cockroaches at my apartment provided geography based clues and said “Awful!” Or talked even instead of scurrying around by the fridge and eating potato chip crumbs.
2. Mrs. Pumpkinklanger: He/She was so funny! Especially since Barry talked in a high voice that to me sounded a little like Julia Child. I used to say that she wore curlers like my mom.
3. Greg’s Mom: I’m pretty sure she only appeared in the episode “Tango Mysterioso”. The look on Greg’s face is priceless when he sees her on the monitor.
4. Nana Rap: Before The Wedding Singer movie made rapping grannies popular there was Nana Rap. Greg would dance along to her clue, the children in the audience would dance, and I would dance watching at home. When she would rap it was just like a big dance party that only rivaled the ending with the dancing on the giant map. I remember that song about the 5 largest islands in the world when her, Rockapella, and Greg rapped/sang that song.
5. Bite and Scratch: A favorite from childhood. Animated cats rapping about geography? Yes please! I danced along to their clues too.
6. The Amazing Disgusting Blob: I really liked this informant as a kid for some reason. I knew it was just a cheesy inflatable puppet in a trash can, but to me it just looked so silly.
7. The Dying Informant (portrayed by Scott Leonard): There were a few other dying informants, but most of the time this role was played by Scott. The over acting by him was so hilarious. I’m not sure who was trying to out act each other him or Greg.
8. Plastic Diver Guy: “He lives a life of danger our underwater ranger the one and only plastic diver guy!” I love his intro with the little cartoon drawings. He was sort of like Mr. Bill. Once the ominous music played at the end of his segment you knew he was going to get hurt in some way like with canned meat or troll dolls.
9. Edwina: She’s a cute character that is Greg’s neighbor who may or may not have a crush on him.
10. The Acmettes: Like Rockapella they did song parodies. They mostly did 1960s girl group wall of sound style songs.