What is the common link between
- an extraterrestrial entity,
- a space traveller,
- Michael Douglas,
- a friend of Thomas,
- a friend of Tony,
- an Army infantry regiment,
- and some naked ladies?
This puzzle is very similar in spirit to [ What do they have in common? ].
The answer is
Gordon $~~~$ (https://en.wikipedia.org/wiki/Gordon)
for the following reasons:
an extraterrestrial entity
Gordon Shumway (TV series ALF)
a space traveller
Gordon Cooper (astronaut)
Michael Douglas
Gordon Gekko (Douglas' character in movie "Wallstreet")
a friend of Thomas
Thomas and Gordon (the tank engines)
a friend of Tony
Gordon Brown (successor of Tony Blair)
an Army infantry regiment
The Gordon Highlanders https://en.wikipedia.org/wiki/Gordon_Highlanders
and some naked ladies
Gordon (title of first album of the "Barenaked Ladies").