In The Invisible Enemy the Doctor uses the TARDIS' relative dimensional stabiliser to reduce the size of the clones. Opening the TARDIS doors in flight might well have damaged the stabiliser in Planet of Giants, a process similar to the shrinking of the TARDIS in Logopolis. The dimensional stabiliser from Drax's TARDIS is turned into a 'shrinking gun' in The Armageddon Factor. The shrinking of the Master in Planet of Fire was caused by experimentation with a new and even more deadly Tissue Compression Eliminator.