At the beginning of Ultima IV Part 2, Mondain (the villain of Ultima and Minax (the villain of Ultima II) appear on Jerry Springer remonstrating with their offspring, Exodus (the villain of Ultima III), until the Avatar, a young man in America watching this on television, is called by "the gypsy" and told they really need him in Britannia.
Which leads into a IV-like set of bogus questions to establish your alignment with "the eight virtues," but which I think are irrelevant here.
Anyway, you wind up in Lord British's throne room and, after looting everything in sight and talking with him to find the secret exit, off you go. Apparently all three of the previous baddies have returned to Britannia and through some hugger mugger they've replaced the eight virtues by new ones. Like, say, "passion" for "compassion" hence the come-on in the screenshot at upper left.
As a game in se, Dude, Where's My Avatar is not spectacular; in fact, though supposedly an RPG, in fact it's it's close to a graphic adventure, the game pushing you to follow through the story and talk to characters in sequence and perform actions with no real choice in the matter, if you wish to unlock the story. There aren't even the random monster fights of the original, nor the multiple and simultaneously pathed quests, to alleviate the linearity of the plot. There are some actual fights in the end game, but the game is calibrated so that if you've done the obvious RPG things (taken everything in sight and spent any money you've earned buying as much crap as possible), you will win.
But it's amusing in its depiction of an altered and depraved Britiannia, and in its parody both of the tropes of Ultima, and of the continuity problems between episodes of the series.
In short, if you are not an Ultima fan, you need not bother (although it would not hurt you to find and play the older games, which have strong virtues); and if you are, you will find yourself chuckling frequently.