The way that Erlang's parents meet and how his mother is rescued varies a lot across traditional storytelling as seen on stage and in recitation. I'll list out the versions I found:
Taiping Geci Recitation: "Splitting the Mountain to Save Mother"/"劈山救母". Erlang lives in Heaven and spends his days hunting. He shoots down a pair of phoenixes and his grandfather the Jade Emperor rewards him with divine liquor. He falls asleep and dreams of his mother, causing him to ask the JE what happened to her. The JE weeps in shame and asks Erlang to seek out the Queen Mother of the West. She tells him that his mother married a mortal, and after having a son, washed the baby's diapers and polluted the seas. Heaven's armies were sent to capture her, but Sun Wukong shut her under Mount Tao. Erlang goes to Taishang Laojun, who tells him about Pan Gu's axe. Erlang goes into the mortal world and finds the axe has gained sentience as a demon. he defeats it and chops open Mount Tao to save his mother.
Bangzi Opera, Cantonese Opera, and Drum Recitations: "Third Princess Goes to the Mortal World"/"三姐下凡". The JE's daughters all go down to the mortal world to view festival lights. Erlang's mother meets his father and falls in love. She escapes from her chaperone, the divine general Hua Guang, and recruits the local Tudi couple to be her foster parents so she can marry Scholar Yang. She gives birth to Erlang, but the JE finds her and sends various gods to capture her. She fights all of them off except Guan Yin, who persuades her to surrender herself. JE imprisons her in the Heavenly Dungeon, where she gives birth to her daughter. Erlang grows up in the mortal world with his father and is teased by his classmates over having no mother. His father tells him about his mother's imprisonment and he goes off to rescue her. Erlang acquires divine arts, weapons, armor, and a horse from the immortal Yuding. He heads up to Heaven, where QMW warns him that JE will send out multiple trials to test his willpower. He'll need to carry two great mountains on his shoulders to capture the 12 suns standing guard over the prison. He does so and frees his mother and sister, and his sister helps him attack JE's palace and force him to agree to pardon their mother.
Han Opera: "Taoshan Cave"/"桃山洞". Erlang's mother falls in lover with a mortal after realizing they're fated to marry. Unfortunately, Yuan Hong's (the monkey demon from FSYY) sister also believes she's fated to marry Scholar Yang. Erlang's mother recruits the local Tudi to help her do some tricks with an old tree that gets Scholar Yang to agree to marry her. Sometime after their wedding the monkey demoness attacks and tries to abduct Scholar Yang. Erlang's mother fights them off and carves her name onto the demoness's face. The demoness runs back to her brother, who attacks Erlang's parents in revenge, but is also beaten back, and during their battle, Erlang's mother brags about her name. Yuan Hong reports her to Heaven and gets help from the Dragon Kings and other gods to capture her. Erlang's mother entrusts her baby son to Taishang Laojun, and the united forces of demonic immortals and gods capture her. Yuan Hong shuts her beneath Mount Tao, where she gives birth to a daughter. Erlang grows up with Yuding. He eats special ox, tiger, and dragon buns, as well as peaches of immortality, then bathes in a mortality-shedding pool to gain his powers. He arms himself and goes to Mount Tao, where he defeats the demons and his dog kills the monkey demoness. He rescues his mother and sister and they head home to reunite with their father.
Puxian Opera: "Third Princess Goes to the Mortal World"/"三姐下凡". Basically the same as Han Opera, except Erlang's mother's rival is a dragon princess. Erlang is considered a freak by his father for having three eyes and given over to Yuding. After Erlang's mother mutilates her rival, the Dragon Kings fight her and imprison her under Mount Tao. Erlang's father is abducted and imprisoned under the sea for refusing to marry the mutilated dragon princess. Erlang grows up and besieges the Dragon Palace. The mutilated princess's younger sister comes out to fight him and they fall in love. She makes peace between him and her family and they free his father. Erlang goes to Mount Tao, where he frees his mother and sister. Their family is reunited.
Hunan Huagu Opera: "Zhang's Second Girl Goes to the Mortal World"/“张二姐下凡". Erlang's mother is the Second Heavenly Princess. She reads some Heavenly Scrolls and notices that two gods are yet to be born and decides to be the one who gives birth to them. She picks as her husband Scholar Yang, who's already married to a woman named Zhao Meirong. She takes Meirong's form and tricks Scholar Yang into believing Meirong is a demon. Meirong goes home to her father and brothers, who are outlaws that rule a certain mountain. Her father has Taoist arts and lights special incense to summon the gods and report this strange matter. The gods discover the Second Princess's identity, but even after having her children, she refuses to leave because she's truly fallen in love with her mortal husband. She is captured and shut under Mount Tao. Erlang is abandoned in the mountains and saved by Yuding. The second part is called "Splitting the Moutain to Save Mother"/"劈山救母". When Erlang grows up, Yuding sends him to a renowned swordsmith couple to forge him a blade that can split mountains. The raw material must be the Ox-King's horn and the fuel must be the essence of golden coal from Mount Mei. Erlang takes the form of the Jade-faced Fox, seduces the Ox-King, and saws off a horn while he's drunk. He then fights the spirit of the Golden Coal. She falls in love with him and willingly sacrifices her essence to fuel the forge. Erlang splits the mountain and saves his mother.
Teochow Opera: "Third Princess Goes to the Mortal World"/"三姐下凡". Erlang's mother goes to Earth to fight a three-headed demon dragon and his lackey, a dog demon. She falls in love with Scholar Yang in the process and takes the form of a huntress to marry him. They have a son. She is summoned back by Heaven and imprisoned under Mount Tao for forgetting her mission. Like in the Lotus Lantern stories, Erlang's father remarries and has another son. The brothers kill a classmate by accident. Erlang's brother is handed to the authorities while Erlang escapes and studies the immortal arts. He finds the very demons his mother was hunting now have their base over her prison. He defeats the dragon, turning him into his spear, then defeats the dog and turns him into his pet. He frees his mother and discovers he has a sister.
Thank you! I'm not familiar with operas at all, so this is a valuable list to people who want to know more about the other variants of Erlang's mom-saving stories out there, outside the premodern ones from the Lotus Lantern Summaries!
