Celtic Guardian is one of the most commonly used monsters of Yami Yugi's Deck. A running gag that happens throughout the series is when Yugi Summons him, he replaces the adjective "Obnoxious" with a different one. Another ongoing joke has the Guardian reference the adjective in some way upon being Summoned or prior to being destroyed. (e.g. "I'm so bamboozled.") He apparently has a grudge against the Blue-Eyes White Dragon for spreading to others that he is a "weak monster", and has developed a complex as a result of that. In a rap battle between Yugi and Jaden Yuki, it is revealed that his name is allegedly Dave, and that he had difficulty stringing together coherent rhymes.
| Episode | Adjective | Quote |
|---|---|---|
| "The Rebexorcist" | Disgruntled | |
| "Yami of Darkness" | Frustrated | "I am so frustrated." |
| "Dirty Dueling" | Bamboozled | "I'm so bamboozled." |
| "Penguin Ex Machina" | Agnostic | "I'm not sure what I believe in." |
| Cr@psule Monsters 3 | Passive-Aggressive | "God, I wish some people would stop posting on Facebook about cats all the time." "Wait, what? Who's doing that?" (Yami) "Oh, you know. Lots of people." |
| Throw Haga From The Train | Sexually Frustrated | "I'm so sexually--oh f*ck, I'm on a train!" |
| Throw Haga From The Train | Obnoxious Celtic Poison Butterfly | "I'm so poisonous." |
| Right In The Feels | Brainwashed | "I'm so whatever he just said!" |
| Valley of the Duels | Obnoxious Celtic Punching Bag | "I'm so..." (cutoff) |
| YGO Kiwami | Obnoxious Kill-Stealing | "That's a nice kill you've got there. It'd be a shame if someone stole it." |