h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

From the details I found, Merckx won the Tour of Spain in 1973

Hinault won the Vuelta in 78 and 83, Giro in 80, 82, 85
Anquetil got the Giro in 60 and 64, Vuelta in 63
Felice Gimondi got Giro in 67,9 and 76, Vuelta in 68 and TDF in 65

However Merckx is also along with Djamolodine Abdoujaparov and Laurent Jalabert one of the only three to win Points competition in all three major tours. So granted he is the only person to have won points and overall titles in all 3 majors.

Given that Fausto Coppi started to compete in the 1940s (winning the TDF in 49 and 52, Giro in 1940,7,9, 52, 53) and Gino Bartali started to compete in the 1930s, ( winning TDF in 38 and 48, Giro in 36,7 46) it is no surprise that by the time Merckx came along in the late 1960s they would need to hang onto a truck!

I have checked these with a couple of different sources and seem correct.

D'oh! I freely admit that I wasn't really sure about these facts. I remembered hearing somewhere that Merckx hadn't won the Vuelta, and so stuck it in assuming someone would correct me _before_ the entry became edited, if I was wrong. I think it was in an article about Jan Ullrich, implying that he could enter the history books properly by devoting the rest of his career to a Giro win, thus completing his set.
I also saw the joke in a magazine article but forgot the names involved and, since I thought I had heard about Merckx competing against Coppi and Bartali, and since they are cyclists of sufficient stature, I used them. I don't suppose you know what the names might actually have been?