A spawn glitch refers to the incorrect placement of any object, including pedestrians, during the loading of an area. Objects can sometimes be seen violently fidgeting and jumping about, pedestrians sunk into the ground or stuck in walls, and even cars can sometimes be seen stuck in another object, sometimes other cars, sometimes constantly sustaining damage until they are destroyed.
Pedestrian Spawn Glitch
In Bayside, along the Southern walkway that leads to the Lighthouse, pedestrians will sometimes spawn with their legs halfway buried in the sidewalk. The section of path seems to be the cause of the glitch, and coding error, in which they are placed, rather than the pedestrians themselves, as CJ can also become stuck in the concrete.
It is interesting to note that the section of path seems to have an unusually high number of pedestrians who spawn there, which the same can be said for the area around the San Fierro Docks.
Car Spawn Glitches
Cars will sometimes spawn stuck inside walls. Being an extremely rare occurrence, the sample size of reported sightings is not adequate to determine areas, where this glitch can be frequently exhibited, or if one particular area is more prone than others, however the glitch has been seen in tunnels around San Fierro.
Sometimes, parked driver-less vehicles will spawn directly on top of one another. Also being a rare occurrence, no known affected areas can be determined, but the glitch has been observed in the Car Park at the base of Mount Chiliad.
The Car Sandwich glitch must not be confused with another similar glitch, wherein vehicles driven by pedestrians spawn inside one-another, whilst in motion. This has been proven to be a direct symptom of the Reversing Vehicles glitch.
Spawn glitches are the result of design oversights and are expected in games as large and complex as those in the Grand Theft Auto series. It is likely Rockstar either did not notice these minor glitches, or felt players would not notice themselves, and their time was better spent addressing other issues within the game.