The two franchises that combined to win the past four Stanley Cup titles made the swap to create more opportunities for two well-liked veterans who didn't fit into their previous team's plans.
Both defensemen spent time in the AHL this month after clearing waivers.
The defending Stanley Cup champion Blackhawks are making a flurry of roster moves before the trade deadline to try to solidify their chances for another title run. On Thursday, they acquired one of the top forwards on the trade market, Andrew Ladd, and sent prospect Marko Dano and two draft picks to Winnipeg. Chicago also got forward Matt Fraser and defenseman Jay Harrison.
The 37-year-old Scuderi played four seasons in Los Angeles from 2009 to '13, getting four goals and 43 assists in the regular season and playing in 50 postseason games. He filled a key leadership role on the Kings' 2012 championship-winning team, immediately taking charge in then-new coach Darryl Sutter's defensive game plan.
But Scuderi left the Kings as a free agent in 2013, taking a four-year, $13.5 million contract to return to Pittsburgh, which drafted him in 1998. After injuries and limited success in his second stint with the Penguins, they traded him to Chicago on Dec. 14.
Scuderi went scoreless in 17 games for the Blackhawks, and he didn't appear to be a long-term fit for the defending Stanley Cup champions. Scuderi has one year left on his contract with a $1.3 million cap hit, but the Blackhawks and the Penguins are both expected to absorb a portion of his salary.
Chicago is retaining 50 percent of their portion of Scuderi's contract and Los Angeles is retaining 15 percent of Ehrhoff's contract.
Ehrhoff had 10 points in 40 games for the Kings this season, his first with the club. The 33-year-old German also sat out as a healthy scratch with the Kings before his AHL demotion this month.
The Blackhawks will be Ehrhoff's fifth NHL team -- and his third since signing a 10-year, $40 million free-agent deal with Buffalo in 2011. The Sabres bought out the deal in 2014.
Jamie McBain has played 40 games for Los Angeles, but was a healthy scratch several times this month while rookie Kevin Gravel got a shot. The Kings returned Gravel to their AHL affiliate in Ontario after acquiring Scuderi.
Fleischmann and Weise are both pending unrestricted free agents.
Fleischmann, 31, has 20 points in 57 games with Montreal, his sixth team. A native of the Czech Republic, he has played in 638 career games and has 133 goals. He has four goals and five assists in 35 Stanley Cup Playoffs games.
Weise, 27, has 26 points in 56 games with Montreal, ranking second on the Canadiens with 108 hits. The Winnipeg native has 85 points in 314 NHL games across six seasons with three teams.
The Canadians will retain 30 percent of Weise's salary, a source told ESPN.
Danault, 23, has scored five points in 30 games with Chicago this season.
Information from The Associated Press and ESPN's Pierre LeBrun was used in this report.