What do you call it, when the character actually does conjure/materialize the object rather than it simply being the most obvious explaination?

"Why is the inside of the TARDIS only that much larger than its exterior?"

The TARDIS is a bad example as it is so big that even the Doctor is unsure how many rooms there are and with each re-generation it changes and adds new rooms. There are several episodes where he gets lost himself or his companions are lost somewhere in it.

What the TARDIS can be best looked at is as portal into a selected part of personal Hammerspace which constantly change. Intresting enough, the Hammerspace is bound to the Tardis and seams to not exist anywhere else as anyone trying to get into it must first locate the TARDIS instead of the Hammerspace it leads too.

Hammer Space - anything to do with Lieutenant Sledge Hammer of an unspecified American city police dept, and his unfeasibly large "amigo". the H Ammer Weapon?