The Inter-Dimensional Doorway is one of Dexter's inventions. Dexter made it in the episode "Deedeemensional".
History[]
Deedeemensional[]
The Inter-Dimensional Doorway's blueprints.
It is unknown what Dexter was attempting to do with it once it was completed, but after he completed it, he released an Inter-Dimensional Monster that ran around his laboratory, destroying everything.
Framed[]
When the popular kids began making fun of Dexter and Mordecai, Mordecai reprimanded them, saying Dexter was way cooler than them for having an Inter-Dimensional Doorway. Showing that Mordecai knows about Dexter's laboratory.
Meanwhile...[]
Dexter had once again used his doorway in hopes of extracting a new discovery from the 5th dimension. Instead what he got was a comic book detailing everything that was going to happen to him on that day.