Seapony posts are posts in which a blogs main character(s) are temporarily transformed into Seaponies (some blogs feature characters that are permanently seaponies, in which case they may change their character into land ponies for a post or two). Such posts are often accompanied by the phrase "Shoobedoo", a reference to singing seaponies which appeared in G1 of My Little Pony.
In "Firefly's Adventure", a My Little Pony special, the 1st Generation Applejack and the human girl Megan find themselves drowning and trapped inside a giant clam shell. It happens. Before they can drown, a group of seahorse-like creatures cunningly renamed "seaponies" release them from their watery prison in a song and dance number revolving around a chorus of "shoo-be-doo, shoo-shoo-be-doo". The kindness of the seaponies is only matched by their cruelty, given that they refuse to bring the small bubble of air to the surface until they've finished their performance...