Under what circumstances would a change to the case name occur when no changes were made to the parties involved?

Question

Given that when a Plaintiff files an unlimited civil lawsuit with a US Superior Court, the name of the Plaintiff and the name of the first named defendant in the complaint are used to form the case name. [Edit: Thank you to @ohwilleke for confirming/clarifying this former assumption]

However, after nearly half a year later, the case name is suddenly changed from being the Plaintiff and the first named Defendant to the Plaintiff and one of the other named Defendants in the complaint.

In light of this, what sort of reason(s) might exist that could explain or justify why this change had suddenly occurred when taking into consideration the fact that no defendants were dismissed, no Plaintiff was added or removed, no new defendants were added or removed, no legal name changes had been made, no spelling mistakes had been identified, and no recent filings could be found that would otherwise explain why the case name had been suddenly changed?

For example:

• Spongebob Squarepants, an individual, files a lawsuit against Patrick Star, an individual, Sandy Cheeks, an individual, and Pearl Krabs an individual, and The Krusty Krab, a California Corporation.
• The Case name assigned by the court upon the initial filing of the unlimited civil complaint is Spongebob Squarepants vs. Patrick Star et. al. and is the case name shown when accessing the case online, when viewing all submitted court filings up until the change and is seen used in all discovery requests and responses.
• Following yet another continued case management conference wherein no trial date has been set, suddenly when accessing the case online, a new case name is shown and reads Spongebob Squarepants vs. Pearl Krabs et. al. while Patrick Star, the named defendant that previously played a role in the case name, is still a party to the case along with all the other defendants.

Alternatively, is it possible for one of the other defendants to request that the court not use their name for the case name and thus result in a sudden change being made without any sort of publicly viewable filing?

[Edit: Question was revised and improved to rule out circumstances that would otherwise not apply.]

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Further elaboration

I remember once upon a time a practicing attorney of 25 years telling me that once a case name has been assigned to a complaint, the case name would not be changed for any reason. So I was confused as to why this could've happened when I witnessed a case, suddenly without warning, started appearing under a different case name when searching for that same case number.

This case had started out with the expected case name based on the Plaintiff and the first named Defendant of the complaint and was shown using that case name in all court documents, in all the initial filings, including the original complaint. But, at some unknown point in time, the case name was suddenly changed for that particular case number and one of the other listed defendants was suddenly being used for the case name even though no amended complaint or similar was filed.

Is that something the Plaintiff could've done or perhaps one of the other named defendants?

Again, as mentioned above, it would be as if all initial documents (such as the ones served), as well as how the case appeared on the LACourt website in the beginning was Spongebob Squarepants vs. Patrick Star et. al. and all of a sudden, 6 months after the Complaint was filed, the case name on the LACourt website suddenly changed and became Spongebob Squarepants vs. Patrick Star et. al. when searching for the case number and being reported with the new case name..

Former Due Diligence

When attempting to do a search on case naming, search results kept assuming I was referring to making legal name changes rather than being able to find any laws or text about how a case name is determined and I was only able to find this thread which explained which name comes first in a case name (the party that files the initial complaint).

Answer 1

There are several reasons that case name might change. Here are twelve of them, roughly in order of frequency:

1. A party is dismissed from the case and hence is no longer a party, so the next person in line becomes the first party listed in the caption.

2. There are several defendants, only some of whom appeal, and only the parties that actually appeal are included in the caption in the appeal. This also happens when not all parties who are part of an initial appeal are parties to a later case in the state supreme court or U.S. Supreme Court because the issues upon which certiorari review were granted only pertain to some parties.

3. A government official or trustee of a trust is sued by name in their official capacity and when the occupant of that office changes, the caption is amended to reflect the new occupant of that office.

4. An entity's name changes during the course of the case, either due to a rebranding (e.g. "X" formerly known as "Twitter") or due to a corporate merger or acquisition, or both.

5. The case is consolidated with another related lawsuit and the other lawsuit is given top billing in the consolidated case caption.

6. A party dies or is legally declared incompetent and their executor or conservator or guardian is substituted as a party.

7. The original caption was inconsistent with the body text of the complaint, or is otherwise misidentified, and the caption is amended to correct the error (e.g. someone erroneously captions the case as against "Apple Industries" when the lawsuit is against "Apple Computer" or puts "J.D. Smith" in the caption when the person sued is actually "J.P. Smith").

8. An individual's name changes during the course of the case (e.g. due to marriage or a religious conversion).

9. A party that was originally listed as a plaintiff is reclassified as a defendant, or vice versa.

10. A complaint that was originally filed as a "direct action" is reconfigured as a "derivative action" or vice versa.

11. There is originally a plaintiff, a defendant/third-party plaintiff, and a third-party defendant. The lawsuit between the plaintiff and the defendant is resolved elevating the third-party plaintiff and third-party defendant to be the primary parties in the case.

12. There is originally a plaintiff, a defendant/third-party plaintiff, and a third-party defendant, then the plaintiff asserts new claims against the third-party defendant.

I'm sure that there are other exceptions that don't come to mind.

When you refer to a case that changes name in the middle, you would properly refer to it as Squarepants vs. Star sub nom. Squarepants vs. Krabs (this often happens in the case of appeals where only some parties appeal at each level, or where an official party defendant changes mid-case). The linked definition states that this term is only used when the name changes in a different court, but this term is also used when a case name changes in the middle the same case in the same court to refer to rulings made when the case had a different name.

a primary defendant is somehow chosen (presumably whomever the Plaintiff has listed first in their complaint, I'm guessing?)

Correct. But sometimes in appellate case law, if one party is a very common litigant, the very short (single party) version of the case name will be the name of a party that is not a common litigant.

For example, Brown v. Board of Education is usually referred to in very short form as Brown and this probably would have happened even if the fuller case caption had been Board of Education v. Brown.