Well... here he is! Check him out in all his lampshade-headed glory! It's Mr Boom! (or "Mr Boon" as continuity announcers would sometimes call him, presumably expecting a full rhyme with "Moon".) I don't remember this one (obviously, since it doesn't involve building a house) and you might notice the watching Earth bit actually comes *after* the guest... but before Mr Boo[m/n] gives us a song.
I'm not too impressed that the opening sequence seems to have been cut off, but I'm glad to see the complete (and rarely-shown IIRC) closing sequence on the end. Notice the date is 1990, so I'd have been 4 or 5 years old at the time... so I guess it could have been one of the episodes I saw. I don't remember that smiley face which sounds like a Cyberman kid though.
Hey, there's one notable fact about Mr Boom's physiology which I totally forgot to mention last time. His nose makes a squeak sound if you touch it. That was what really put him on the map for me as a kid so I'm at a loss to explain why I forgot it when I made the earlier post. And there's the name, Andy Munro. Guess it's the same guy then. I'm glad about that.
Other great things about this video include Mr Boom's use of the word "wheech" (or however you spell it), and the fact that the storyteller wears a spacesuit when he's outside, but the entrance to the Dome is just a cardboard door that won't shut properly.
So, in conclusion... thank you TributeToThePast... whoever you are!
6 hours ago