Anything is Possible, part 50 The 2nd Doctor leaves the relative
safety of his TARDIS only to emerge in yet another TARDIS.
The 4th Doctor feared he, and his young companion, Adric, may have been caught in an infinite regression shortly before his regeneration in the episode Logopolis.
Curiosity may not have killed the Kat, but what may it do to a second Doctor on board?