Icahn in Ackman: "He's the quintessential example that on Wall Street, if you want a friend, get a dog."
Ackman on Icahn: "What I can tell you is, this is not an honest guy, and this is not a guy who keeps his word. This is a guy who takes advantage of little people."
Those belligerent sentiments seem to have changed, though, with Ackman even raising the possibility that two of the financial world's most aggressive activist investors actually could team up.
Read MoreBig money activism: Helpful or harmful?
"There is a much greater possibility that we are on the same side than the opposite," Ackman said.
The Journal account ironically attributes recent comments that Icahn made to CNBC as helping set the reconciliation wheels in motion.
Read MoreCarl Icahn defends Ackman, slams Lipton
Icahn said Ackman's move to team with pharmaceutical company Valeant to take over Botox maker Allergan did not appear to be illegal.
"We have our differences, but I never said he's not a smart guy," Icahn said.
Read the full Journal story here.