The Replacement Dimension is the dimension in the multiverse that Rick Sanchez and Morty Smith traveled to in the episode "Rick Potion No. 9" after escaping Dimension C-137.
In the episode Morty's Mind Blowers is suggests that Rick and Morty might have left this dimension when Morty intercepted a highly organised conversation with three Squirrels (Which eventually lead to a squirrel apocalypse) although this must still be confirmed.
History
It is a dimension that is apparently identical to their original Dimension C-137, a dimension in which Rick accidentally turned everyone into Cronenbergs.
Being too lazy to change things back to normal, Rick traveled to an alternate dimension where his counterpart had been lucky with the situation (and did fix it) and was also conveniently killed by a failed experiment alongside Morty. When they arrived, they took the dead bodies of that dimension's versions of themselves, buried them in the backyard, and continued in this timeline. It is possible though unconfirmed that, after Morty had a problem with a group of squirrels, he and Rick had to leave for yet another dimension. If this did happen, it presumably did sometime before "Morty's Mind Blowers".
The name of this current dimension is currently unknown.
Appearances
It is possible but left ambiguous that, before the events of "Morty's Mind Blowers", Morty and Rick started living in a different dimension.
Season 1
- "Rick Potion #9"
- "Raising Gazorpazorp"
- "Rixty Minutes"
- "Something Ricked This Way Comes"
- "Close Rick-Counters of the Rick Kind"
- "Ricksy Business"
Season 2
- "A Rickle in Time"
- "Auto Erotic Assimilation"
- "Total Rickall"
- "Get Schwifty"
- "Big Trouble In Little Sanchez"
- "Interdimensional Cable 2: Tempting Fate" (Cameo)
- "Look Who's Purging Now"
- "The Wedding Squanchers"
Season 3
- "The Rickshank Rickdemption"
- "Rickmancing The Stone"
- "Pickle Rick"
- "The Whirly Dirly Conspiracy"
- "Rest and Ricklaxation"
- "The Ricklantis Mixup" (only briefly in the pre-intro scene and post-credits scenes)
- "Morty's Mind Blowers" (briefly, in a Mind Blower)
- "The ABC's of Beth" (possibly)
- "The Rickchurian Mortydate" (possibly)