Terri Flagstaff is Fiona Flagstaff's little sister. She has appeared in a few episodes.
Terri is a book worm. She can be a little rude but will apologize for her behavior when it is the right thing to do. she hates Buzz and in the episode "mole lotta truble" calls him "Buzzered breath" but in the Halloween episode, she seems to defend him.
- Terri does know about Fiona's dinosaur side but only after Fiona told her family.
- Terri is a huge bookworm and is seen in one of the episode reading at the dinner table against her parents wishes, so they then take the book away from her.
- Terri hosted a Halloween party in the Halloween episode.