The Pebble and the Penguin/Land Before Time crossover
This one would work very well, the animation styles are the same.
Description:
The Gang, Ali and Shorty are frozen in ice, and when they thaw, they find out that they are in the future from Marina. She begins to show them around their valley, but soon the gang finds out that Red-Claw, Screen and Thud were frozen in the ice too, and they have thawed out too. The gang, and penguins have to work together to stop the three sharpteeth from killing everyone in the valley.
If I did write this fanfiction, Marina and Littlefoot would be the main characters, then Gwynne and Cera would be the supporting characters.