From the Super Mario Wiki
“Sleep makes me... feel better!”
Beef Cloud is a character that appears in Mario & Luigi: Dream Team, as one of Big Massif's four Hooraw disciples that must be fought in the Beef-Off. He is a giant, round Hooraw with white cloud-like hair and pants, a relaxed face and is constantly sleeping.
In battle, Beef Cloud does not attack, does not have any Hooraws to support him, nor does he have to be defeated within certain conditions. Instead, Beef Cloud is constantly sleeping. As he sleeps, he heals himself in real-time (roughly once every five seconds), rather than every turn - even during Mario's attacks.
Due to Beef Cloud's constant healing, Mario has to attack as quickly as possible (likely by using normal attacks instead of his Luiginary Attacks) to inflict more damage than his foe can recover. After taking several hits, the giant Hooraw will wake up for a short time. Eventually, once he can no longer heal himself (because of attempted damage), Beef Cloud can then be attacked and easily defeated.
Of the Hooraw disciples, Beef Cloud has the lowest POW and SPEED, but has the highest DEF and second-to-highest HP.
Names in other languages