It all started on Saturday when Reynolds, 42, posted a photo of himself and Hugh Jackman having a friendly chat.
"Happy #BestFriendsDay to Jake Gyllenhaal! (Not pictured)," Reynolds wrote.
Of course Jackman, 50, had to then get in on the fun. He posted a photo of himself and Reynolds embracing. However, if you look closely, you'll notice Jackman seems to be trying to politely escape the enthusiastic grip of his pal.
"Stage 4 clinger. #bestfriendsday #HiJake," Jackman said.
Gyllenhaal, 38, wasn't about to let the day pass without taking a turn roasting Reynolds. He posted a photo of himself and Jackman holding drinks and looking dapper at a party, where they were clearly having the best time ever.
"Happy #bestfriendsday to Ryan Reynolds (not pictured)," Gyllenhaal, 38, wrote.
At that point, the fun spilled over into the comments section.
“True story...Hugh is just under 5 feet tall,” Reynolds wrote.
They even declared a truce earlier this year and agreed to make ads for each other's companies. However, after the Best Friends Day roasting, it appears all bets are off.
Jackman got the last word...for now.
"Looking forward to our dinner on the 12th. Without ... not pictured," the "X-Men" star commented on Gyllenhaal's post on Saturday.
That's one dinner we'd love to RSVP to!