Norma-ler, or Once-lerxNorma, is the most popular heterosexual pairing in the Once-ler fandom and probably as close to canon as it gets in a romance-free movie like The Lorax.
In the 2012 movie, Norma 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 than canon showed, in fact many have come to believe that the Once-ler is Ted's grandfather. 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 offscreen and eventually leading to the conclusion of them having a love life in the past.
Many headcannons have been developed about this paring, fanfiction and fanart is also very common. However it is not a proven cannon pairing.