I remember reading some of my uncle's old comics a long time ago - these were from the 80s or earlier. One scene that stands out is a scene where a bunch of Marvel heroes were in a large alien base. I seem to recall that it was abandoned and they were using it as their base at the time.
Spider-Man is crawling along the ceiling, wondering about what all the pipes are for (and notes that they make crawling on the ceiling fun or challenging, and are good for hiding) when he overhears the X-Men planning to leave the base to join with Magneto.
Spidey is detected (I think by Prof X) and proceeds to open up seven kinds of beating on the X-Men during his escape, and is about to tell Captain America what he heard when Xavier blanks out his mind.
I think Doom was involved somehow, too.
Does anyone recognize this scene? What comic was it in?