Newton the Gnu, codenamed Agent Silent G, is an O.W.C.A. agent first appearing in "Agent Doof". He later appeared in "Phineas and Ferb Save Summer", and fought the scientists with the other agents. During both fights Newton endured a beating because after being punched by one scientist, he crashed into a wall at the hands of another.
- Gnu is another name for wildebeest.
- He is titled Agent Silent G for the silent g in "gnu". Coincidentally, Agent Silent G doesn't seem to make a sound.
- In Brazil, the g in "gnu" is pronounced so Newton had his name changed to Gnewton.
- Newton's identity remained secret until Doofenshmirtz put it up on his blog.
- According to his secret file, he tends to keep to himself. He is known for his full luxurious beard. And he is looking for a new secret identity since it was revealed by Dr. Doofenshirtz.(Where's My Perry?)
- In "Where's Perry? (Part Two)", another gnu agent is seen.
- "Agent Doof" (First appearance)
- Where's Perry? (Part Two) (another gnu agent)
- "La Candace-Cabra"
- "Phineas and Ferb Save Summer"
- Where's My Perry? (Agent File)