The Larry universe is made up of several parallel universes.
Background
There are at least three main universes including Larry's original universe, 20th century real-world earth, and WD universe. At least two of the universes are not directly connected leading to two seperate Larry Laffers the original Larry Laffer and the Larry Laffer (WD). Larry Laffer (Reloaded) is a bridge between both universes with some memories of the past universe, but reliving/reincarnated into the new universe (he meets the older Larry Laffer from original series as well, who has apparently time traveled/slid into that universe as well (see Larry Laffer (Short Man)).
Sierra World
Sierra World is the parallel universe Larry originated from aka Sierra World. Multiple parallel universes make up the Multiverse.
LSL1-3 (except ending of 3), LSL5-6 and 7-8 (MCL-BOB) more or less take place in this universe.
Real-world
He mysteriously was brought to real-world earth through a magical portal on Nontoonyt Island. The parallel universe is close to our own.[1] This Earth is a parallel universe to Larry's universe.
LSL1-3, LSL1SCI (VGA/EGA), LSL5-6 are games (and/or films) programmed by or starring Larry Laffer in this universe. As seen at end of LSL3 and discussed in The Official Book Of Leisure Suit Larry and The Authorized Uncensored Leisure Suit Larry Bedside Companion.
WD universe
The Wet Dreams universe takes place in yet another parallel universe to that of the original series. The original games exist telling the old adventures, but which happened in a separate 'parallel universe' (that time traveling Larry, and his clones do not remember).
According to Lefty, Larry went missing decades ago not long after events or LSLR, also indicating that original Larry exists in a parallel universe (or at least he lost track of Larry).
El Rey has seen visions into the parallel universe of the old games as well. He warns Larry that he doesn't even want to know happened to him in those universes.[2]
Larry remembers the events from Reloaded however he appears to be new clone of that Larry who died after Reloaded, and brought back through the underground Larry factory with only some of that characters memories. He apparently even experienced a version of Lust in Space in his previous life, having been abducted by aliens before he awoke in the factory. However, most of his memories are limited to his experiences in Reloaded.
A version of Larry Lovage exists in this universe as well.
Lesser universes
LSL1SCI universe
This is either a parallel universe to original Larry timeline and/or a film/game reinactment of original story with new actors (see The Official Book of Leisure Suit Larry. Larry who appears in the game is the original Larry either repeating history or reinacting his role from the original game. The Missing Floppies are acknowledged, and other self-referential referenced to other games in the series.
Reloaded universe
Yet another parallel alternate universe version of Lost Wages. Larry from original series yet again deja vu like experience of repeating history, and has vague memories of Leisure Suit Larry 4: The Missing Floppies. And memories of his nephew Larry Lovage. But he also runs into another parallel world sliding/time traveling version of himself as well.
This Larry apparently died at some point after Reloaded, and possibly after Reloaded’s version of Lust in Space, and is cloned and wakes up in underground factory in Wet Dreams future’s parallel universe, however with incomplete memories from previous experiences (and zero memories from his parallel self from the original universe).
Alternatively this universe was a separate parallel universe version of the Reloaded universe sharing a very similar events to Reloaded but with slight differences. Either way a Larry died was reborn in the Larry factory. A dream/memories Larry has shows AGI style alternative bathroom in Lefty’s may indicate what the previous past of this universe looked like. A death scene also shows the factory (in agi style graphics) cloning Larry yet again and returning him to the world if he dies in Lefty’s by electrocuting himself.