Chalmers Santiago is the 42nd episode in Season 1 of Clarence.
While Clarence spends a lazy Sunday playing an 8-bit adventure game called DRAGON’S CUSP, Mary asks him to return some mail to the guy across the street, “Chalmers Santiago,” whom they’ve never seen. Clarence makes it his mission to befriend the mysterious neighbor, only to find out it’s someone he knows quite well.
Clarence has been watching TV all day when his mother comes in and tells him to drop off some old stuff at the thrift store. Before leaving, Clarence digs through the box of stuff and finds several old things (including Lil' Buddy), and at the bottom of the box, he finds a game console called the "PLAYTHANG", which he plugs into the TV, turns on, and loads a game called "Dragon's Cusp". After playing only two levels, he gets bored again and asks his mother what he could do next.
She tells him she has mail for the guy across the street, Chalmers Santiago, who's getting extremely expensive power bills. Clarence goes across the street and knocks on the door, but there's no answer, so he slips the mail under the door and begins to walk away when he sees that the mail is gone from underneath the door.
He runs back across the street (also causing Randy who's on a bicycle to run into a set of trash cans along the way) and looks out the window back at the house, at which his mom comes over with binoculars, curious about what Chalmers looks like. When the person inside opens the door for a pizza delivery, the pizza boy (who is Joshua) blocks the door. However, they're able to see a pair of hands, but it also reveals that the person is very short.
Clarence then makes several attempts to see who Chalmers Santiago is; pretending to be another pizza delivery boy, repeatedly knocking on the door, etc. In a final attempt, after many, Clarence knocks on the door madly, many times, and then sees that a fence gate opened, so he has access to the backyard. Creepy music plays as Clarence stumbles upon an empty pool (which is very similar to the one in the intro of the show), and when he sees that the back door is slightly open, he pushes it open enough so that he can get inside. The interior of the house is wrecked, but Clarence reasons that it looks very much like his own house, but backwards.
He treks through the broken-down house, not finding any signs of life, but seeing almost every room from his own house completely backwards. When he comes to what would be his room in his own house, all he finds is a chewed-up mattress and a music box playing a slow, childish tune. He follows a wire down the hall, hearing strange noises all the way. When he finally comes to the end, he looks into a room with a giant TV, large speakers and a chair sitting in front of the TV. He hears mumbling as he approaches the chair, and right when he's behind the chair, the TV screen flashes "GAME OVER" and the chair tips backward to reveal Belson, with the dialogue of "UUUGGH! It's so unfair! Everyone's cheating!".
When Belson and Clarence see each other, they both scream for a few seconds before Clarence says "Oh, hi Belson!". Belson asks what Clarence is doing at the house, and Clarence asks if he moved. Belson says that Chalmers Santiago is some guy works with his dad and that he bought this place thinking it would be an investment, but no one wanted to live in the dumpy neighborhood, so he just used it as his crib and told Clarence that the place was pretty lame and moldy but was okay as long as you stayed out of the darkness. Belson then tricks Clarence into thinking that he's going back with Clarence to his house, but shuts the door on Clarence on the way out.
Clarence wait's til' after dark, then he realizes about a plug that goes from Chalmer's House to his house.He unplugs the cord, Belson screams and Clarence thinks it's his dog. Back Inside, Clarence and Chad are playing video games and Mary's asleep. Chad know how to set it up, but some static shows up on the TV. Chad catches Belson and he lies saying he came to play Dragon's Cusp.