Mummipokey
Mummipokey is the second boss in World 2 of New Super Mario Bros.
Mummipokey is a mummified Pokey, who is a vertical, spiky cactus.
In this battle, Mummipokey pops up at different heights and places. Mario or Luigi must Wall Jump on his head three times to beat the boss and access World 3. It is also possible to just wait for him to pop up at a low height and hop on his head normally.
However, if Mario wants to access World 4, the plumber can defeat Mummipokey as Mini Mario. Mario must Ground Pound Mummipokey's head three times as Mini Mario to access World 4.
Mummipokey is possibly a Skellokey, an undead Pokey who happens to look rather similar to Mummipokey. It is also possible that Mummipokey is a Pokey Mummy, another undead Pokey with a similar name; however, he looks little like a Pokey Mummy.