"Ser un pulpo" = To be an octupus*

To be all arms.

"Se pasa mucho con las chicas. Es un pulpo"
"Paso de ese tío. Es un pulpo"
"Todos los pulpos han venido hoy a la fiesta, qué asco"

Note: There is one funny expression in Spanish which translates into "To be completely lost" both literally and figuratively -->
"Estar más perdido que un pulpo en un garaje". Obviously, this "pulpo" refers to the orginal animal and points to the fact that octupuses belong to the sea. That's why they feel at a loss in such a place. A most graphic image :D