A recent federal court order gets the basics of entity law representation right, but it's pretty murky on exactly what entity is involved.  The case involves a claim of trademark infringement in which the plaintiff, International Watchman, Inc., sued OnceWill, LLC.  The order explains: 

In OnceWill's Motion, OnceWill indicated that it “is a sole proprietorship consisting of proprietor Ryan Sood.” (Id.) OnceWill's Motion also showed that it was filed by Ryan Sood, acting pro se. (Id.) The Court granted OnceWill's Motion that same day.

Subsequently, also on November 12, 2020, Plaintiff filed its Motion, requesting that the Court strike OnceWill's Motion and reconsider its order granting the requested extension of time for OnceWill to respond to Plaintiff's Complaint. (Doc. No. 13.) Plaintiff asserts that OnceWill is a limited liability company (“LLC”), not a sole proprietorship as OnceWill represented. (Id. at 2.) In support of this assertion, Plaintiff provided a printout from the Washington Secretary of State's website showing that OnceWill is listed as an LLC. (Id.; Doc. No. 13-1.) As a result of OnceWill's status as an LLC, Plaintiff argues that OnceWill only can maintain litigation or appear in court through an attorney and cannot file pleadings or motions in Court on its own behalf pro se as it has attempted to do here.

INTERNATIONAL WATCHMAN, INC., Plaintiff, v. ONCEWILL LLC, et al., Defendants., No. 1:20-CV-02290, 2020 WL 7138650, at *1 (N.D. Ohio Dec. 7, 2020).
 
As I have noted previously, though some people don't like the idea, the need for an entity to be represented by counsel is generally understood to be required.  The court corrects the initial misstep of allowing the LLC's apparently sole member to appear pro se for what he claimed was a sole proprietorship. If it's a properly created LLC, it is an LLC.  
 
So, what, again is an LLC? I am glad I asked.  An LLC is a "limited liability company," which is an entity distinct from a corporation.  At least, that's what state law tells us. Some courts like to merge the two, as evidenced in this case.:
“The law is well-settled that a corporation may appear in federal courts only through licensed counsel and not through the pro se representation of an officer, agent, or shareholder.” Nat'l Labor Relations Bd. v. Consol. Food Servs., Inc., 81 F. App'x 13, 14 n.1 (6th Cir. 2003). “This rule also applies to limited liability corporations.” Barrette Outdoor Living, Inc. v. Michigan Resin Representatives, LLC, No. 11-13335, 2013 WL 1799858, at *7 (E.D. Mich. Apr. 5, 2013), report and recommendation adopted, 2013 WL 1800356 (E.D. Mich. Apr. 29, 2013); accord Perry v. Krieger Beard Servs., LLC, No. 3:17-cv-161, 2019 U.S. Dist. LEXIS 27311, at *2 (S.D. Ohio Feb. 21, 2019) (“[L]imited liability companies may not appear in this Court pro se and, thus, may only appear through a licensed attorney admitted to practice in this Court.”); Hilton I. Hale & Associates, LLC v. Gaebler, No. 2:10–CV–920, 2011 WL 308275, at *1 (S.D. Ohio Jan. 28, 2011) (“[A] limited liability corporation is another example of an artificial entity that should retain legal counsel before appearing in federal court.”).
Id. (emphasis added). In this instance, it is accurate that the representation rule that applies is the same for LLCs and corporations, but that does not make LLCs and corporations the same.  Really! 
 
It really does seem proper to me not to allow pro se representation of entities, even when they are owned and operated by a single person (though I have noted elsewhere that I would be okay with pro se representation for administrative matters, as long as allowed for by statute or rule).  Note that here, Mr. Sood almost certainly does not want to be a "sole proprietorship" because if he were, he could be held personally liable for OnceWill's trademark infringement. (Of course, it is possible he might be, anyway, but one certainly would not want to make it easier to be held personally liable.)  In fact, the plaintiffs here might have be wise to request amend their complaint to also name Mr. Sood, individually, to the lawsuit, in case the court did allow the pro se appearance. Appearing pro se, it seems to me, suggests personal liability.  
 
Lastly, a comment on the last citation from the excerpted part of the order:  What is an artificial entity?  Are certain entities real?  Like maybe general partnerships? But even those partners can be corporations and LLCs.  Or are is this distinguishing natural persons from "artificial" entities?  I imagine this is intended to be similar to the "fictional person" concept for the corporation, thus further justifying the requirement that an entity must be represented by an attorney. But if so, it would be good to be clear about that.   
 
Oh well.  Such is life.