Gubson

Gubson was a Skeleton horse owned by Wilbur Soot and Prince_Oeduard (Pyrocynical). The horse appeared in the second season of Skyblock, but Every 30 Seconds a Random Item Spawns, where he was the first mob spawned.

Random Item Skyblock Challenge (with Pyrocynical) / minecraft skyblock but every 60 seconds is a new item
After Prince_Oeduard received a skeleton horse spawn egg, Gubson was placed into the world. Due to the Wilbur Soot's and Prince_Oeduard's fear of his life being cut short, Wilbur Soot quickly names him.

Later when Mario is spawned, Wilbur Soot becomes Gubson's owner.

Later on, Wilbur Soot receives a dolphin spawn egg, which he uses. Immediately, the newly spawned dolphin jumps off the edge and also pushes off Gubson, killing them both.