"A collection of insults 18" joke

A few shrimps short of a barbie.
A few spoons short of a full set.
A few straws shy of a bale.
A few tiles missing from his space shuttle.
A few tiles short of a successful re-entry.
A few too many lights out in his Christmas tree.
A few volts below threshold.
A few yards short of the hole.
A flash of light, a cloud of dust, and… What was the question?
A gross ignoramus - 144 times worse than an ordinary ignoramus.
A hop, skip, and jump from success, but to get there he’d have to give up chewing gum.
A kangaroo loose in her top paddock.
A lap behind the field.
A little light in his loafers. (Apparently offensive to some? Sorry.)
A looney tune.