The only 20K attraction Disneyland ever had was a walk-through exhibit in Tommorowland that used the props from the movies. The same thing would later be seen in Disneyland Paris.
Disneyland however did have the subs ride which was extremely similar to WDW's 20K but it was not a 20K ride. Just a sub ride. It is right now going under a rehab that will add a nemo overlay for the attraction and will reopen the attraction.
Before I continue with that, I will note that there is a new 20K ride. At Tokyo Disney Seas. It is supposed to be pretty cool from what I heard and it does solve all the problems from the WDW ride. But you couldn't have just updated the WDW version. The Tokyo Disney Sea version is actually a suspended monorail that never once comes in contact with water.
Now, back on the WDW ride and its relation to Disneyland's. If the Tokyo update was out of its league, then how about the Disneyland one? The answer is simple really. Due to spacing issues in Disneyland, the Sub attraction was actually built under Autopia. It was done so that space was ultimatly saved and there was no large and ugly showbuilding taking up a huge amount of room. The Magic Kingdom is a much larger park so when the 20K ride was built, there was no reason to fit the building in a tight space. So in the end, the MK version of the subs ride ends up taking up 1/2 of fantasyland while the Disneyland Subs are hidden under tommorowland.
But that also caused this problem. The Magic Kingdom version had no hope. Castmember hated working on it. That is why it got closed for over 10 years. But the whole thing came down as of late and now lets see... Fantasyland can double its size now. Just to note even more on the scale of the size of the Fantasyland attraction, 3 E-rides have a good chance of managing to fit into 20K's plot. I mean, it is just mind-boggling amazing how much room this ride took. I personally hope the Imagineers will turn this new plot into a nice expansion to the WDW's Fantasyland. It is rather pathetic on the size and look of Fantasyland. It needs help.
Now Disneyland's subs attraction. It was closed to make away for the flop called the "New Tommorowland". Nothing actually replaced the subs, it was just closed. (well any update on the subs would require wheelchair access to be implemented). But now look, The Subs attraction at Disneyland happens to be a lucky attraction. It is one of the few attractions that is almost impossible to remove or replace. So, the imagineers are working on the new Nemo ride. It may not fit in with Tommorowland but the return of the subs altogether should bring rejoice to everybody.
But not only that in Disneyland, it seems that all those new rides there are causing a chain reaction. Currently there are plans for replacing the 3-D theatre and reopening the people mover as well as moving the astro-orbiter.
And beyond that, George Lucas wants to update Star Tours.
Too bad the Magic Kingdom isn't getting a treatment like this. I personally think that both Fantasyland and Tommorowland need huge overhauls and expansion projects.
