Mo is a character in the Land Before Time films and television series. He is a colorful Opthalmosaurus, which is referred to as a "swimmer" (which also describes any animal in the series which swims) in the films and TV series.
In his debut appearance, Mo was washed away from the Big Water (the ocean) and into the Great Valley. Littlefoot was the first to meet him, and they immediately befriended each other. Mo thought Littlefoot said "Yittle-foot". When Cera, Ducky, Petrie and then Spike met him, Littlefoot revealed to them that he and Mo had declared themselves to be "Mud Brothers". Mo then told his story, and the children went to their parents for help in returning him to his home. The adults were wary of helping a strange aquatic creature from beyond the Valley, so the children set off to help him on their own. When they had reached the Big Water, after several days, and met Mo's family, Mo invited Littlefoot to see what it was like under the water, and Littlefoot became mesmerized by the sight, so Mo carried him back up to the surface before he could drown. They then said goodbye, and Littlefoot and the others returned to the Valley.
In other filmsMo has made a couple of cameo appearances in the later sequels. In The Land Before Time X: The Great Longneck Migration, he can be seen briefly jumping out of the water during the "Adventuring" musical number. He can also be seen jumping out of the water and saying "And fly!" during the song "Flip, Flap and Fly" in The Land Before Time XII: The Great Day of the Flyers.
Mo is incredibly playful and enthusiastic, as he often plays practical jokes on others, though in good humor. He is amiable, and quick to befriend a new acquaintence. When he detects potential danger, he can be loyal and brave, as evidenced when the Sharptooth Swimmer first appeared in Journey to Big Water, and Mo tried to warn the others, then went down to ward the swimmer off. It is also seen later, when the swimmer attacked the children again, this time on their journey to the Big Water. While the children hid in a log, Mo used himself as bait to lure the sharptooth away, after which Littlefoot and the others thought he was lost. He survived, however, and returned to them the next day.
Littlefoot immediately liked Mo, and constantly commented on how he found him to be "so much fun". Ducky, Petrie and Spike liked Mo upon impact as well, but Cera found his boisterous and rambunctious antics irritating at first. Later, the morning after Mo had disappeared with the sharptooth swimmer, Cera confessed to the others that she really liked Mo, but didn't like the fact that everyone paid so much attention to him, and thought him to be fun; she wanted them to enjoy her presence as well.
Mo is bilingual, in that he can speak both the language of the land-dwelling herbivores, and the language of the sea creatures, like himself, which the land-dwelling creatures don't apparently understand. This is evidenced when Mo asks a crab to release Cera's horn, in his own language. Mo is not the only bilingual or multi-lingual character in the Land Before Time series. Chomper, who becomes a main character in the series, is able to speak the herbivore-language and the Sharptooth-language, and Scuttle, a sand-creeper who can also speak the herbivore-language as well as his own.
Like Petrie, Mo speaks in broken English and often refers to himself in the third person.
- Even though brother is a male term, he still calls Ruby, Cera, and Ducky his mud brothers too.
- He is one of the characters that appears in a movie then appears again in the TV series like Hyp, Nod, Mutt, Ali, Doc, Bron, Shorty, Tippy, Tippy's herd, and Guido.
- Mo can sing to insects as he sang to either grasshoppers or crickets.
- Mo, like Petrie, refers to himself in third person.
- Mo has a skin color similar to the Jurassic Park Gallimimus seen in a few games and toylines of the series.