Childhood in Guardia
Glenn was born in Guardia, possibly in Truce or Dorino, in an unknown year prior to 590. His best friend was Cyrus, who was several years his senior. Glenn was often a victim of indiscriminate bullying from the children his age due to his passive nature, which Cyrus often had to step in to stop. When Cyrus suggested that he learn to fight back, Glenn explained that he doesn't wish harm on anyone, even if they hurt him. Cyrus, seemingly resigned, called him a marshmallow.
Several years later, when Glenn was a teenager, Cyrus declared his intent to enlist as a royal knight of Guardia. He suggested that Glenn join him, but Glenn expressed doubts about his potential to be a good knight. Cyrus pointed out that Glenn was better than him with a sword, but Glenn explained that he didn't think he could bring himself to hurt others. Nonetheless, at some point, Glenn made the decision to take Cyrus' advice and enlisted as well.
The Squire
Following their talk, Glenn eventually came to Guardia to serve as Cyrus' aide. During this time, he would journey with Cyrus on many adventures - including a battle with the Frog King which yielded the retrieval of the Hero's Badge, a magic sigil that showed one's true strength and aided the wielder of the Masamune. Glenn would also meet and befriend Queen Leene, who concerned herself greatly with his and Cyrus' safety.
The Battle with the Fiendlord
In the year c. 590 AD, Cyrus and Glenn departed to face the Fiendlord Magus, who had been plaguing Guardia with conflict with his army of Mystics. Together, they traveled to the top of the Denadoro Mountains to claim the Masamune from Masa and Mune. Cyrus single-handedly managed to defeat the twin Mystics, and they offered him the use of the sword out of admiration for his skills. Shortly thereafter, armed with the legendary weapon that could defeat him, Cyrus confronted Magus atop a high cliff. Glenn stayed out of the fight but was present to witness it. Cyrus charged Magus but was blown back by his powerful magic, which consequentially shattered the Masamune into two pieces. As a wounded Cyrus urged Glenn to run and protect the queen, Magus cast one final spell that killed Cyrus in a violent blaze. Glenn picked up the broken hilt of the sword, yet remained too afraid to attack. Ozzie then suggests that Magus give the boy "a more fitting form". Amused by the suggestion, Magus cast another spell that transformed Glenn into an anthropomorphic frog form and flung him off the mountain. Glenn, now transformed into a frog-like creature, awakens on the bank of a river at the base of the mountain as the Hero's Medal floats in the water nearby.
The War with the Mystics
In the ten years following his curse, Glenn (now calling himself "Frog") is consumed with regret and self-loathing over his own weakness in the fight against Magus and blames himself for Cyrus' death. He fails to return to Guardia and instead lives in self-imposed exile, allowing everyone to continue speculating on the disappearance of Cyrus and hope for his eventual return. He dwells alone in a hidden grotto deep within the Cursed Woods.
The Disappearance of Queen Leene
In the year 600 AD, Frog learns of the disappearance of Queen Leene and remembering Cyrus' final request to him, returns from exile in search of her. Although the search was called off when Marle was found in Truce Canyon and mistaken for the queen, Frog continues his investigation alone. He arrives at Manoria Cathedral, where he happens upon Lucca being ambushed by a Naga-ette. Frog rescues her by striking the beast down and proposes that they work together to rescue the queen, but Lucca expresses discomfort over his frog-like appearance. Frog is disheartened and prepares to leave without them, but Lucca asks him to stay. Despite her aversion to frogs, both she and Crono decide to journey deeper into the Cathedral with him. Together, the three defeat Yakra and rescue the queen and the real Chancellor, whom Yakra had been impersonating. After returning to Guardia Castle, Frog denies any praise from the royal family and blames himself for the queen's abduction, before departing to return to his life of solitude once again. As Crono and his friends intercept him at the steps of the castle, he remarks that Crono shows talent as a swordsman and implores him to find him should he ever want to train. If she is in the party, Frog will comment on Marle's uncanny resemblance to the queen. Finally, after Frog departs, Lucca will walk a few paces after him and remark on her fondness and a newfound respect for him.
The Hero Returns
During the unknown amount of time that Crono and his party were away, Frog lost track of the Hero's Badge. In the Japanese translation, this is due to excessive alcohol consumption causing him to drop the badge in a tavern in a drunken stupor. The badge is found by a young boy named Tata, who is then praised as the legendary Hero who will vanquish Magus and end the war, and is more than willing to go along with the lie. Frog learns of this but explains to Crono and company that he wants nothing more to do with the Masamune, the badge, and has no hope of defeating Magus. He states that there is nothing he can do and is content to wallow in his misery. After recovering the Hero's Badge from the cowardly Tata as well as the two shards of the Masamune, Crono and the party confronts him, insisting that he is the only one who can wield the Masamune and defeat Magus. At first, Frog is unwilling to help them, citing his own weakness. They then discover the hilt of the blade among his belongings, which leads them to Melchior. When the sword is reforged, they return to Frog's home and present him with the restored Masamune, asking once more to help them defeat Magus once and for all. This time, Frog remarks that he has much to think about and asks them to stay the night. As the party sleeps, Frog looks over the sword and recalls his time as Glenn, including the fate of Cyrus and wondering whether he is strong enough to wield the sword. In the morning, Frog seems reinvigorated with a desire to avenge his friend and joins the party permanently.
The Battle in the Fiendlord's Keep
Crono, Frog, and their ally proceed to the Magic Cave, the only way to reach the Fiendlord's Keep. Finally taking hold of the Masamune, Frog uses its power to cleave the foot of the mountain in half, opening up the long-sealed pathway to Magus. After facing his generals - Slash, Flea, and Ozzie - Frog and the rest proceed to the inner sanctum where they find Magus in the midst of a mysterious dark ritual. Magus battles them with his powerful magic, but Frog uses the Masamune to break his nigh-impenetrable magic barrier. Their battle weakens Magus, causing him to lose control of his ritual - revealed to be a spell that summons Lavos. The creature begins to wake up too early, and the space-time distortion it causes sends them all hurtling through time.
Facing Magus
In the time era of Antiquity, the party learns that the mysterious "Prophet" is actually Magus in disguise. Following the destruction of Zeal, the party will encounter Magus on the North Cape, and Magus offers Frog his long-awaited chance for revenge. If Frog manages to slay him, this ensures spell on him will be eventually broken and he will change back to his human form. This decision will result in a one-on-one battle between Magus and Frog. However, Frog may choose to deny the opportunity, stating that revenge won't bring back Crono or Cyrus. This decision will result in Magus joining the party.
It is up to the choice of the player whether to slay Magus or allow him to join the company. This decision will impact the rest of the game, as well as the form in which Frog appears in some endings.
The Hero's Grave
In the year 1000 AD, Frog and company discover the restless spirit of Cyrus haunting a location near Choras known as the Northern Ruins. In 600 AD, they are able to repair Cyrus' grave which puts his spirit to rest. Proceeding to his final resting place, Cyrus' spirit appears and empowers the Masamune, making it stronger than ever. The conversation with the ghost of his former friend also brings Frog considerable closure, as he finally stops blaming himself for the past and is able to move past the traumatic events of his past.
Endings
Several endings of the game, particularly those that show the departure of the main characters back to their own time periods, have two variants based upon Frog.
Should the player decide to fight Magus the second time on the North Cape in the Antiquity, the spell on Frog would be broken, but not until the end of the game. When the group says their farewells on the last evening of the Millennial Fair, a tall, green-haired knight approaches them, thanking them for their help. Marle and Lucca realize that he is actually Frog transformed back into a human, and cannot help but admire how handsome he is.
A similar ending happens if you choose to fight Magus a second time and leave Crono dead. It starts the same with Marle and Lucca celebrating the last day of the Millennial Fair, then as you go to the two pods the gate bursts open with Gaspar, Ayla, Robo, and a long green-haired man. Ayla demands the Time Egg, but before Gaspar gives it to them he jumps back into the gate. The man explains the situation, then Marle and Lucca realize that was Frog now Glenn. Lucca then wants to follow the party using the Epoch for the sole purpose of hitting on Glenn, quoting: "Nya ha ha! Hey Frog! Why didn't you tell us you were a dish?"
If Frog spares Magus, the game ends with him looking off into the horizon on the peak of the Denadoro Mountains, reminiscing about Cyrus.
Defeat Lavos after giving the Masamune to Frog, but before fighting Magus, and the ending sequence will begin at Lucca's House. The group will celebrate their victory over Lavos. In the middle of the party, Frog slips away, saying he has unfinished business. The scene then switches to Magus' Castle. Frog moves through the Castle, easily killing Slash, Flea, and Ozzie. He moves through the castle traps and confronts the keep's master, Magus. The two battled to the death, knowing one of them will not walk away alive.
The sequence ends with an unknown silhouette perched on top of the keep. It is never revealed whether it is Frog (who has had the spell broken by Magus' death) or Magus who walked away from the victor of the duel.
Another ending shows Marle post-Lavos, confronting her father. Both she and her father have some unseemly attributes. They croak and hop like frogs, suggesting they were descendants of Queen Leene and Frog, although the relationship between the knight and his liege is said to be strictly platonic.
An ending exclusive to the FMV of the PlayStation and DS releases depict Frog transforming back into a human form. A large ceremony including all of the nobles of the court and the royal guard is held for him, and the King, wielding a jewel-encrusted sword, knight him. One note about his design in this ending is that his hair has been cropped fairly short; in the flashback prior to his transformation, his hair is depicted as much longer and is clearly tied into a long loose ponytail from a rearview.
