Mattis T. Monkey is Rianna F-Fiona's monkey apprentice.
Mattis was born when her male counterpart goes to the NEXO Knights world. Mattis was left under Clay's watchful eyes while her master, Rianna F-Fiona, is away fighting Jestro and Morro, before he is reformed, with Ryan and the other NEXO Knights. She kept being cheeky and hid from Clay so he couldn't boss her around. She and Rianna were good friends and heroes to the NEXO Knights and she helped them with some deeds. She refers to Rianna as "Master Rianna".
- Oh, why do I always have to stay behind under Clay's watch?
- Maybe if I hide from Clay he can't boss me around.
- Thomas is being stolen?!
- Let me help, Clay. My monkey moves are so good I can be excellent at finding things.
- Clay, if I know Thomas, he's probably already thought about his escape plan.
- Come on, we need to hurry and find Thomas.
- [after seeing Sci-Ryan in his Flutterbat form] That's not Sci-Ryan... that's Sci-Rybat.
- [sees Clay 2] Are you up for some fighting monsters, Clay?
- Maybe the swan is the princess named Odette, Master Rianna.
- Thomas, Clay might be in trouble.
- Clay, let's just go.
- Let's see. If Matau's master is a PKE Meter, then where could he be?
- Thomas, where are you?!
- Sunburst is Starlight Glimmer in the Genderbent universe?
- Odette is Rigby's sister?!
- Let's go find Thomas.
- Matau? How did you get that arc reactor in your chest?
- Come on.
- Aw. Young love.
- I may not know who Sunvix is but she is bad news.
- Let's go. We need to hurry and find Thomas.
- You look so awesome, Wolfgang.
- Uh, excuse me, ladies but have either of you seen a blue tank engine with a bad wheel?
- When did Lightning say the word "Sha" for something?
- Guys, we've gotta keep going.
- Who is the girlfriend of Ryanset anyway?
- But how are we gonna get past all those cars?
- Looks like the castle of the two sisters is still new.
- Cody? What happened to Twilight and Equstria?
- Let's just go.
- What is it, Budgie?
- Is Ryan in the Golden Queen's body, Clay?
- Ryan looks so good in the Golden Queen's body.
- We're been spotted! The walls are closing in! Hurry! Help me and Clay prop up Morro, Master Rianna or we're toast!
- [after Clay 2 tells her he's supposed to say that] Oops! Sorry, Clay!
- [after Matau asks Mattis who is her twin sister] Oh, she's Beatrice.
- Percy would never say that.
- Hello, Odette. I'm Mattis.
- I don't believe it. Optimus doesn't even recognize us.
- So. The Ryan in this timeline is a Changeling? But how did he become one?
- We have to find the AllSpark.
- This will not end well.
- Rigby. We never knew that you and Odette are related.
- Lance, you've got to pony-up!
- Boy. Ryan is ok as a Dazzling.
- We've got to help Derek fall in love with Odette.
- Thomas, go! Save the AllSpark!
- Holy Mos Eisley! William! Are you ok?
- Wait. Why does Indigo have a pendant?
- I think she's a human.