DOTT is particularly special for being a sequel to Maniac Mansion, a Gilbert game I had briefly played somewhere on the original NES.
The entire Maniac Mansion game is also included in playable form within DOTT, on a virtual computer found within the game's environment.
I remember first playing DOTT on the PC and discovering the embedded Maniac Mansion. Up until that point I hadn't realized I was playing a sequel to that NES game I'd long forgotten about.
They're fun games, quirky with a great sense of humor and playful innocence about them.