So yeah, stuff you probably don't care about but I think it's fun....
1) "The Web of Fear" is pretty much the start of the so-called U.N.I.T. Dating Controversy in Doctor Who. And no, it doesn't have anything to do with the Doctor finding someone to go out with on the weekends. The U.N.I.T. Dating Controversy a debate among fans who like to try to peg down when certain Earth-set stories are happening. Originally, the production team intended for the Third Doctor's era to be occurring in the "near future" -- then about the late 1970's to early 1980's since the show was actually airing in the early to mid-1970's. The problem is that prop designers and costumers kept using items which were clearly current and not even slightly fashion forward. The writers also kept messing things up and forgetting that the stories weren't set in current time. This led to a bit of confusion but it all starts with "The Web of Fear" because all future stories date from this one. In the later story "The Invasion" Lethbridge-Stewart shows up again and tells the Doctor that the events in "The Web of Fear" were four years earlier. Following this "Spearhead from Space" -- the story that began the Third Doctor's era -- indicates that not that much time has passed since "The Invasion" -- not more than 12 months or so.
The "Web of Fear" aired in 1968 but there are some slight indications that he writers intended for it to be taking place in the "near future" of about 1974. Again, the problem is that the costumes and technology are very 1968. The mentions here are so slight that most people automatically think the story is taking place in 1968. There are, however, indications that "The Invasion" was supposed to be taking place in 1978 but, again, clothing and technology are clearly compliant with 1960's and not the late 70's. Those 1978 indications, however, are also so slight they can be easily ignored.
So the point of all of this, if there is one, is that all the problems with figuring out when the UNIT based stories were occuring can be traced back to this particular story. It's also something that still gets touched on in the modern series. As a tribute to the confusion in the Season Four story "The Sontaran Stratagem/The Poison Sky" the Tenth Doctor comments that UNIT has come a long way since he worked with them "In the 70's.... or was it the 80's? I can never remember."
2) The Yeti/the Great Intelligence were slated to return for one, final story in Patrick Troughton's final season. Fraser Hines had been heavily urged by his agent to break away from Doctor Who after three years to do other things. As he was having great fun working on the show, however, and enjoyed his co-workers in Troughton and Wendy Padbury (who played Victoria's replacement, Zoe) he was reluctant to do so. Finally, he agreed and told the production team he would be leaving the show but he dragged his feet on deciding when to leave. At one point it looked as though he would leave near the end of the 1968-1969 season and a story outline was created for an episode to give his character of Jamie a send-off. In the proposed story the TARDIS would finally land in Scotland not long after Jamie first left (totally ignoring the fact that the Scots were pretty brutally supressed by the English for several years after the Battle of Culloden, which is when Jamie was picked up). Jamie would meet a bonnie lass and the Doctor would discover that the Great Intelligence and it's Yeti robots were active in the area trying to gain power. Jamie would get mind controlled by the Great Intelligence for a while but eventually the Doctor would free him, destroying the Great Intelligence once and for all in the process. The dying Laird of Jamie's clan would then ask him to become Laird and Jamie would feel his duty was to his clan and would decide to stay, marry the young woman he had fallen in love with, and take up the duties of leader of his clan.
The story would be scrapped when Hines discovered that Troughton was leaving at the end of the season and so decide to stay on until the end and leave at the same time Troughton did.
3) After redesigning the Yeti to be more fierce and fearsome the production team felt it would be a good idea to kind of publicize this fact. Therefore, at the end of the preceding story, "The Enemy of the World", they showed a little blurb that was specially filmed with Patrick Troughton. The scene was actually shot on the Underground sets used for "The Web of Fear". Sadly, that footage, along with most of "The Enemy of the World" and "The Web of Fear" is missing. An enterprising computer animator on YouTube who goes by the handle tardistimegirl, however, has created a reconstruction. And it is awesome. Check it out...