Mr. "Ant" Tenna (referred only as Tenna) is a 27 year old 3D-rendered humanoid figure with an old TV for a head, lacking any facial features aside from a wide, often-grinning mouth and a long, pointed nose. His attire consists of a flashy red suit with twin coattails, a long yellow tie, black pants, large cartoony white gloves, and bright yellow dress shoes. He is gigantic compared to both King and Queen, but can change his size. He is a TV monster.

Tenna is an upbeat and energetic show host who thrives on entertaining his audience by both flattering and challenging his contestants. Beneath his lively persona, however, he is deeply insecure and egotistical, prone to panicking when things don’t go as planned. He recalls fondly how, as a television in the real world, he once brought Kris, their family, and friends together to play games and watch shows. Now feeling abandoned, Tenna struggles with feelings of worthlessness and loneliness, and fears that he’s no longer interesting and that he’ll be discarded. While outwardly upbeat multiple interactions with Kris and Susie, reveal these insecurities of failing as an entertainer, as his sprite can be found lamenting on if the lighters are even enjoy his games or not and wishing that Kris would give him guidance on what to do before panicking when hearing footsteps. To this end Tenna appears to be somewhat fearful of Kris as when his sprite is confronted in third Sword Route level, he attempts to remind Kris that he followed their orders like he was instructed to and fearfully questions if he is going to be turned off again. If Kris is wearing the Shadow Mantle after that encounter, Tenna's normal boss battle dialogue slightly changes to him nearly revealing that Kris created this Dark World.

Throughout Chapter 3, Tenna creates multiple quizzes with answers relating to Kris’ family in the past, showing a very big sense of sentiment. However at multiple points Tenna reminds and alludes to Kris of their parents divorce as a possible misguided way of trying to relate to them. This is supported during his mental breakdown in the Doom Board, where Tenna's demeanor changes to an oddly apologetic tone after the failed cooking minigame, with it appearing to trigger traumatic memories of Toriel and Asgore having a heated argument he was present for.

While Tenna is outwardly patient, he can be driven to vindictiveness as after his falling out with his former business partner Spamton, Tenna includes various amounts of insults or slights at the business man throughout his games or quizzes, at one point urging Susie to kill a model based off of Spamton's head in a bonus mini game or directly blaming Spamton for his inability to use technology.

When confronted about his age, Tenna adamantly denies being "old." After the Trio discovers Toriel trapped inside a toy capsule and intending on leaving his Dark world entirely, he spirals into panic and reacts by imprisoning them in capsules as well. His outbursts often turn destructive; he lashes out and fires his employees in bursts of anger, driven by his overwhelming fear of being left behind and forgotten.

Despite this, he is shown to have a kind heart. Part of his motivation for forcing the Delta Warriors into his show was simply so that he could entertain them. He has a strong desire to entertain and bring people together. While he even expresses frantic concern over Toriel, doing everything he can to assure she doesn't wake up, this is because he worries his overall plan of appeasing the Knight may fail. His desire to entertain, while apparent enough to make one trust him, is also rooted in wanting to help the Knight succeed in taking Toriel. This conflict of wanting to help the Knight but needing the attention from the Lightners is what ultimately makes him change for the better.

Tenna is also seen to be rather enthusiastic and patient, as if you lose the physical challenges multiple times, he'll always end his dialogue with "One more try! Let's CHALLENGE again!" demonstrating his confidence and faith.