- The issue of just what constitutes cheating was raised in Friendly Hostility. Fox is devoted to his boyfriend, Collin, but his bisexual colleague Derringer springs a kiss on him, just to see what it's like. Fox is outraged. However, he's even more outraged when Derringer questions Fox's kissing skills... and so Fox kisses him again to prove his aptitude. On the Friendly Hostility blog (doubling as The Rant), fans varied between "kissing is cheating" to "it was just a kiss" to "kissing usually counts, but there was no affection behind it, so it doesn't." Some fans even suggested that it might be good for Fox and Collin to break up following this incident, since they didn't think it was psychologically healthy for Collin to only have one romantic/sexual partner in his lifetime and he needed to "see other people" rather than remain exclusive to Fox.
- Nerf NOW!! had Sniper-tan cheating on Pyro with the Spy, after an argument. Spy later produced ambiguous evidence that Pyro had had an affair with Engie-tan. Subverted in that nether of them were caught... at least by each other.
- Eva apparently cheated on Davan of Something*Positive several times while they were together, before he finally caught her doing it with her abusive ex-boyfriend.
- Kyle also cheated on PeeJee numerous times - this proved to be a really bad idea when she found out.
- Zigzagged. Dave and Terezi were in a relationship, but he found out she was also seeing Gamzee. However by troll standards Terezi did nothing wrong, since her relationship with Dave was redrom (romantic) while her relationship with Gamzee was blackrom (Foe Yay) which trolls consider two vital and distinct types of relationships. Dave however still broke it off since by human standards she was cheating and she had tried to hide it from him.
- Played straight, however, with Rufioh, who is stated fairly explicitly to have cheated on Damara with Horuss. Suffice to say it doesn't end well for any of them.
- Eerie Cuties: This applies to Layla's ex-boyfriend, Kade Whiteclaw, which is lampshaded by the Hellrunes, here, after he's caught in the act of cheating on Layla. A few strips later, Layla also points it out, right before decking him.
- In Distortion Nuzlocke, Johnny catches Mr. Fangen cheating with his wife on Erika.
- NJ from Electric Wonderland had a girlfriend, Suē, who cheated on him with 27 guys. After she flirted with NJ's closest male friend, Torro, he told NJ about it, setting off a chain of unpleasant revelations that resulted in NJ breaking up with Suē. His public revelation of her affairs subsequently land everyone in a conflict of Gamergate proportions.
- Jerry from Contest Jitters cheats on his bodybuilding girlfriend when he finds a more conventional beauty.
- In El Goonish Shive, this plays a big role in Susan's backstory. Susan's father cheated on her mother, and Susan discovered this by walking in her father with the other woman. This event left Susan a bit distrustful of men for a while. It also led to her dyeing her hair, as her natural blonde hair reminded her of her father's mistress.
- You can trigger a bad ending in Violet if you use a command to have sex with, kiss, or simply hug your ex 6Julia.*** I hope you get a disease ***
- A frequent topic of Saturday Morning Breakfast Cereal.
Your Cheating Heart / Webcomics