The earliest found ironic use of the phrase “that would be funny” was on January 1st, 2019 in the former official Discord server of r/okbuddyretard, “whenthe.” Discord user samppa asked a moderator to give everyone the moderator role, saying “hah hah that would be funny!’” (shown below, left). The next day, Discord user don sancho asked to smell another member’s feet, imitating the Yoshi Haha copypasta (shown below, right).
The first found image macro using the phrase “that would be funny I think” is an October 4th, 2019 post on r/okbuddyretard by user Unknowncows. The post gained over 500 upvotes before being archived (shown below, left). “that would be funny I think” took off on the subreddit after a November 10th, 2019 post by err_mate received over 36,000 upvotes in nine months (shown below, right).