Norma-ler, or Once-lerxNorma, is the most popular heterosexual pairing in the Once-ler fandom and probably as close to being canon as you can get.
Norma in the 2012 movie is Ted Wiggin's grandmother and is the one who told him about the Once-ler and how to get him to talk about what happened to the Truffula Valley, as well as buying marshmallows for him to give to the Once-ler.
Many people took this a bit further than would be seen by a non-fan, in fact many have come to believe that the Once-ler is Ted's grandfather for these reasons. Norma seems to know quite a lot about the Once-ler in the movie, thus triggering the idea that connections between the two had been made off set and eventually leading to the conclusion of them having a love-life. The Once-ler also mentions that he "knows a thing or two" about girls, which many fans had found interesting seeing as in most of the movie he is alone.
Many headcannons have been developed about this paring, fanfiction and fanart is also very common however it is not a proven cannon pairing.