In this post I will distinguish between the "gospel of Mormonism" and other sectarian versions of Creedal-Christianity, where humor, joy and laughter are often absent or rejected. The fact is the New Testament gospels actually never mention Jesus smiling or laughing. To be fair though, D. Elton Trueblood tried to argue in his book The Humor of Christ that Jesus told jokes and had a sense of humor. But most priests and pastors never discuss D. Elton's theory and focus more on reminding you that "you're a sinner" and on fearing God's wrath. Watch this short video titled Orthodox Christianity is Depressing, discussing how most traditional imagery of Jesus in Christiandom is not very cheerful to get the idea. Only in Joseph Smith's restored gospel in LDS Scripture does Jesus appear smiling to his disciples in 3 Nephi 19:25, 30.
In Mormonism you have a more joyful representation of the gospel (the "message") in that life in the flesh is not to be despised, because all flesh is composed of spirit-matter (see D&C 131: 7-8): and so you do not have this sour faced framework of "spirit against flesh," since in Mormonism the fleshly body itself is a spiritual materiality, bodily instincts and all; which turns "dionysian" joy and laughter, fun and dancing and celebrations of life in the body, into a spiritual activity rather than a "sinful" one. So rather than the pursuit of sour faced somber piety like the body-despising sectarians (who often sought to repress all joy in the sensory body), the pro-American Joseph Smith basically pursued "life, liberty and the pursuit of happiness."
Joseph Smith "said ... to Mr. stout that Adam did not commit sin in eating the fruit" in 1841. For Adam only transgressed, so we are not as humans cursed with a permanent "sinful flesh" as claimed by Augustine's Original Sin dogma, which is nonsense and was rejected by Joseph (see Article of Faith #2). Joseph Smith instead dictated new scripture that declared that Adam was a mighty Archangel and he taught that Adam recieved the priesthood prior to earth. This radically shifted the framework away from the sectarian view in the Creeds, that saw Adam as sinning which cursed all human flesh: so that to be "holy" and/or "right with God" one needed to repress their instincts, appear pious, with celibacy as the highest spiritual ideal (if you were able). This body despising mentality was based on an underlying wish to escape one's alleged sin-cursed body, leading to sour faced self-flagellating life avoiding "pillar saints" and permanently celibate Catholic priests (that we still see to this day in the Catholic Church). By shifting the framework to a non-sinning Adam and Joseph saying Adam did not curse humanity with a "sin virus" -- but instead Adam did good by giving mankind the opportunity to experience joy and happiness in a body -- Joseph Smith had completely flipped the script and turned a life lived joyfully in the body itself as the way to connect with the divine or be "right with God."
Joseph Smith completely rejected the core doctrines of the sectarian Creeds. In his restoration of all things, he rejected their core doctrines like the Fall, the Trinity, and Hell. For example, in D&C 19, Joseph explained that hell language in scripture is only metaphorical and in D&C 76 he taught Three Degress of Glory in the afterlife. This liberated the minds of his followers and removed the chronic mental stress many of them felt as former Protestants when they were terrified that a loved one or friend could be tortured in hell for not going to the right church or for not believing in the correct dogmas. Joseph Smith removed all of that mental anguish, all that pain and fear, with his doctrines; and thus he restored a sense of joy to being human again. For example, a relative of mine, Benjamin Franklin Johnson, grew up attending a Protestant church and while "attending these services, he was taught the principles of heaven and hell, and began to be 'afflicted with the idea of a future punishment, with literal fire and brimstone.'[3] Johnson said that this idea created great fear and anxiety in him until he found the Gospel of Jesus Christ [i.e. the LDS Church]" (Source). It's kind of hard to have fun and enjoy life when you're constantly tormented with the thought of you or your friends and loved ones, who don't belong to the right church or subscribe to the correct Creed, are going to be tormented forever in hell. I am personally saddened when I continue to meet many Creedal-Christians up to this day who are heavily burdened and drained of life daily by such hell fire fear mongering by their priests and pastors. Joseph Smith liberated my Pioneer ancestors from this yoke by instead casting a metaphorical canopy of joy over the horizon with a smiling Christ and gradations of heaven.
Joseph taught that Adam fell upward so that mankind could pursue happiness through navigating oppositional forces and experience joy in a body of flesh (see 2 Nephi 2: 25). This meant that Adam's "one act" was part of a greater plan all along: which was for pre-existence spirits to gain bodies of flesh in order that they would have joy in their bodies of flesh! In fact, rather a Father God without a body and no passions (as taught in the sectarian Creeds), Joseph declared that God the Father has a body of flesh and bones (see D&C 130:22); and rather than demanding extreme repression like we see with the pillar saints, Joseph Smith explained that actually "God is more liberal in his views"; and the same fun and joyful "sociality" among us here as humans would exist among us in the heavens among the embodied Gods (see D&C 130: 2; Abraham 4 and D&C 132).
In my view, Joseph Smith's life-affirming joyful theology was a mirror reflection of his own nature being a cheerful person with a sense of humor. These articles below go into more detail about Joseph Smith's personality and temperament:
