Wendy O. Koopa is one of Bowser Junior's 6 (now 7) siblings who is first seen in The Koopa Kids! She was voiced by Chilly Jimenez, but she was later voiced by Elaina Keyes. She is really mean, swears constantly, and acts like a spoiled and sassy brat. She is the youngest of Bowser's family.
- "Turn on the lights!"
- "I'm Wendy!"
- ONE SISTER!"
- EXCUSE ME?!?"
- "It's going great look all clean!"
- "I'm gonna clean the couch!!"
- "Get outta the way!"
- "All clean!"
- "We're coming Mom shut your damn mouth!"
- Her personality is somewhat similar to Lola Loud from The Loud House, Angelica Pickles from Rugrats, Princess from Harvey Beaks, Pleakley from Lilo and Stitch, Cupid from Fairly OddParents, and Sarah from Ed, Edd, and Eddy.