See Bobbin Threadbares Face
It is possible to see what Bobbin looks like under his hood. Just play in
the difficulty setting "expert" until Cob lifts Bobbin's hood and only in this highest
difficulty setting you will find out how he looks underneath it all.
I could just show you a picture of Bobbins face here but there has to be some challenge left
when the game is that easy anyways. Right?!
Loom in other games
Cobb, the henchman of Bishop Mandible also appears in Monkey Island and hangs around in the Scumm Bar and tells you about Loom (if you ask him).
I don't know how Cob managed to die in Loom and reincarnate in Monkey Island.
The seagull from Loom also appears in Monkey Island 1 (behind the ScummBar), Monkey Island 2 (on the tree with the map piece) and
Day of the Tentacle (at the chimney).
In Space Quest IV you can buy a game named Boom
The Inscription on Lady Cygna Threadbare's Gravestone:
In Memory of
LADY CYGNA THREADBARE
Destiny shall draw the Lightning
Down from Heaven; roll its Thunder
Far across the Sea, to where I
Wait upon the Shore of Wonder,
On the day the Sky is Opened
And the Tree is split asunder.