Dexter's Lounge is a 30 second long mini segmet used in season 2, episode 35; Dee Dee's Rival/Pslightly Physco/Game For a Game.
In this mini segment, Dexter exits his lab after a hard day's work, and accesses an underground malt shop called "Dexter's Lounge." Then he walks through the dining area and lots of kid characters are seen sitting down and drinking milkshakes. Then Dexter goes up to the counter and yells "science shakes for everyone!" Then everybody holds up their science shakes.
Dexter is working in his laboratory and then he takes a break by going down a secret elevator which leads to a bar. The bar is filled with other kids there, the kids who are recurring characters are Douglas E. Mordecai III who is just sitting there, everyone who are at the table next to him, and Mandark and Dee Dee who are on a date. Dexter goes up to the table where a Bartender Robot is working and he tells him to take a break it's his shift how, and he puts on a sign that says Dexters Lounge in the same format as the Dexter's Laboratory sign from the theme song and says "Science shakes for everyone!" and then everyone holds up their science shakes.
- Mandark and Dee Dee were seen on a date even though Dee Dee hates Mandark.