Famous cases of multiple papers by the same author published in same issue of same journal I have been wondering if there are many cases of an author having published two (or more?) papers in the same issue of the same journal. I vaguely recall having seen one or two cases like this, maybe be old papers, but cannot vividly remember. I have the impression such a situation would make sense should the two papers be in the same topic, say, one is sort of a (substantial) continuation of the other, for instance (given the fact that in Mathematics there is some pressure against publishing too often in the same journal). I am of course asking this question for papers having a sole author (or maybe the same set of authors).
 A: Leonhard Euler (1707-1783) published frequently in the journals of the St Petersburg Academy, usually several papers per issue. This continued even after his death, as he had a substantial backlog of mathematics - the final paper appeared in 1830. These represent about half of his published work.
https://scholarlycommons.pacific.edu/euler-spap/ has an index, from his first such paper

Problematis traiectoriarum reciprocarum solutio (1729). Commentarii academiae scientiarum Petropolitanae, 2:90-111.

to his last

Intégration d'une espèce remarqable d'équation différentielle dans l'analyse des fonctions à deux variables (1830). Mémoires de l'académie des sciences de St.-Petersbourg 11:131-137.

There are several issues where Euler was the only contributor in the mathematical section. Note that in the actual journal texts, the tables of contents attribute several papers to Eiusd., short for eiusdem, meaning the same as above; typically, that is L. Euleri.
The topics are sometimes closely related. In 1751 his papers include 88 pages on integration of rational differential forms, followed by another paper of 51 pages presenting an easier method for the same. But his other two papers in the same issue are some conjectures in number theory, and another on the motion of fluids under heat.
A: Abel had two papers in the first issue of Volume 1 of Crelle's Journal. A look through the Table of Contents of that volume will turn up several other instances of an author with more than one paper in an issue.
A: Not sure this counts, it's a famous one ... A. Einstein had 3 papers in Annalen der Physik 1905, Folge 4, Band 17: On pages 132, 549 and 891. Now, there's also another overall numbering in which this corresponds to Volume 322, in which these are assigned to different "issues", but I'm not sure whether those correspond to how the articles were distributed originally ...
A: Edoardo Ballico published (until now) 404 articles in the International Journal of Pure and Applied Mathematics. He published many times two or more articles in the same issue.
For instance, in 2009 he published four articles in "Int. J. Pure Appl. Math. 57 (2009), no. 4,"
A: Roger Howe famously filled an entire issue of Pacific Journal of Mathematics (volume 73, no.2, 1977) with 8 different papers. (Also, Euler...)
A: This is a physics example rather than a mathematics example, but Albert Einstein did this many times.  I believe on many occasions he in fact published multiple papers in the same issue of the same journal for different journals (often doing this several times in one year).
For example, someone above gives the example of the papers he published in 1905 but in fact in that same year, he also published multiple small review articles in the same issue of Beiblätter zu den Annalen der Physik on multiple occasions.
He likely did this again many other times although I don't have time to trawl through all the journal articles as he published more than 260: for more information, see the Wikipedia article.
As another theoretical physics example, I think Edward Witten has also done this at least once.  For example, Global aspects of current algebra and Current algebra, baryons, and quark confinement are two separate papers, both of them published in Issue 2 of Volume 223 of Nuclear Physics B.  He may also have done this with more mathematical papers in Communications in Mathematical Physics but I can't remember.
A: This case is not famous at all, but I think it deserves to become at least better known, so...
Beso Pachuashvili, gifted mathematician who passed away this year, is hardly known to anybody. His insights into Hopf algebra theory and monoidal categories still await proper understanding. Most notably he had envisioned certain variant of the fact that in commutative monoids of a monoidal category tensor becomes coproduct for other kinds of limits. In case of equalizers, this opened up one possible approach to the construction of cohomologies in monoidal categories. In mid eighties he had some interaction with Drinfeld on the topic, I wonder if Drinfeld can recall what information did they exchange back then.
The entire issue 2 of Volume 72 of the Journal of Pure and Applied algebra (from 1991) is occupied by his two papers: "Cohomologies and extensions in monoidal categories" (doi:10.1016/0022-4049(91)90027-Y) and "Some properties of cohomologies in monoidal categories" (doi:10.1016/0022-4049(91)90028-Z).
A: In the first issue of Fundamenta Mathematicae, 1920, Wacław Sierpiński has 13 single-authored papers and 1 joint with Stefan Mazurkiewicz. In the same issue Mazurkiewicz has 3 addtional single-authored papers. Kazimierz (Casimir) Kuratowski has 3 single-authored papers and 1 joint with Zygmunt Janiszewski (a posthumous publication for the latter). The papers are not parts of bigger ones. Sierpiński also contributed several open problems to the first issue (one jointly with his student Tadeusz Felsztyn); Mazurkiewicz (alone) and Kuratowski (jointly with Bronisław Knaster) contributed 1 problem each.
Sierpiński and  Mazurkiewicz also were editors-in-chief of the journal at the time, taking over after the death of Janiszewski, who got the idea of the journal and prepared the first issue for print.
Fundamenta were supposed to concentrate on set theory and topology, the specialties of  the still-new Polish school of mathematics, so it is natural that the specialized journal featured so many contributions by then-active top Polish mathematicians. Especially the first issue, which was also meant as a kind of an introduction of the Polish school to the broader mathematical community. But even in later pre-war issues there are often multiple papers by Sierpiński and/or other authors.
The papers can be viewed and downloaded for free at https://www.impan.pl/en/publishing-house/journals-and-series/fundamenta-mathematicae/all/1
