Wis. Stat. § 802.07
Section 806.02(2) provides that the plaintiff may move for default judgment according to the demand of the complaint. This section gives no indication that the appellations "plaintiff" and "defendant" may be reversed for purposes of a counterclaim. Pollack v. Calimag, 157 Wis. 2d 222, 458 N.W.2d 591 (Ct. App. 1990). A defendant may not join opposing counsel in counterclaims, but claims may be asserted against counsel after the principal action is completed. Badger Cab Co. v. Soule, 171 Wis. 2d 754, 492 N.W.2d 375 (Ct. App. 1992). This section does not contain mandatory counterclaim language but, res judicata bars claims arising from a single transaction that was the subject of a prior action and could have been raised by a counterclaim in the prior action if the action would nullify the initial judgment or impair rights established in the initial action. A.B.C.G. Enterprises v. First Bank Southeast, 184 Wis. 2d 465, 515 N.W.2d 904 (1994). When collateral estoppel compels raising a counterclaim in an equitable action, that compulsion does not result in the waiver of the right to a jury trial. Norwest Bank v. Plourde, 185 Wis. 2d 377, 518 N.W.2d 265 (Ct. App. 1994). In an automobile injury action by an injured party naming the driver of the other car and the injured party's own insurance company as defendants, the court was not competent to proceed on a default judgment motion by the insurer against the other defendant when the insurer had filed an answer, but no cross claim against the other defendant. A default judgment entered in favor of the insurer was void. Tridle v. Horn, 2002 WI App 215, 257 Wis. 2d. 529, 652 N.W.2d 418, 01-3372. Cross-claims are generally permissive in Wisconsin. Wisconsin Public Service Corp. v. Arby Construction, 2011 WI App 65, 333 Wis. 2d 184, 798 N.W.2d 715, 10-0878. The general rule in Wisconsin is that when a defendant may interpose a counterclaim but fails to do so, the defendant is not precluded from maintaining a subsequent action on that claim. A.B.C.G. Enterprises, 184 Wis. 2d 465 (1994), established a narrow, common law exception to the permissive counterclaim rule as a means of reconciling the tension between that rule and claim preclusion. A counterclaim is compulsory only if claim preclusion would otherwise apply and a favorable judgment in the second action would nullify the judgment in the original action or impair rights established in the initial action. Hull v. Glewwe, 2019 WI App 27, 388 Wis. 2d 90, 931 N.W.2d 266, 17-2485. But see Teske v. Wilson Mutual Insurance Co., 2019 WI 62, 387 Wis. 2d 213, 928 N.W.2d 555, 17-1269. When a defendant obtains judgment on a counterclaim, the judgment extinguishes the defendant's right to recover on other counterclaims arising from the same transaction. Bankruptcy Estate of Lake Geneva Sugar Shack, Inc. v. General Star Indemnity, (1999). Landing in A.B.C.G.. Soup: The Compulsory Counterclaim Trap. Bach. Wis. Law. Mar. 2006.