General: inflatable
Inflatable characters or props are those that are intended to be filled with air. This is a close cousin to the inflation tag. While that tag refers to characters actually being inflated, this tag refers to characters or props that are intended to be. (The "inflation" tag may not apply if they're presently deflated!)
Common features include valves, visible seams, latex/rubber/vinyl, and other clear signs of hollow-ness or artificial construction.
