I know many of them went to West Point around the same time. Do we know about their collegiate interactions with each other? Were Lee and Grant friends? Did Stonewall ever prank Custer?
Lee was 15 years older than Grant, and likely never met him before the war; however Lee was the Superintendent from 1852 to 1857 so would have been known of by virtually every military officer in U.S. service at that time. Grant was at the Academy three years ahead of Jackson, so it is doubtful they were buddies but certainly would have known each other. Sherman was two years ahead of Grant at the Academy, so likely missed Jackson there but would undoubtedly have known him in military service due to his long career prior to the Civil War.
Custer pranked everybody, but only entered the Academy in 1857 and graduated in spring 1861.
Note that both the U.S. military establishment and the Academy itself were very much smaller than today. Graduating classes sizes from Westpoint in the first half of the 19th century were only a few dozen; the size of a small high school today. Only in 1900 was the authorized enrollment at WestPoint increased to 481
Union General Custer met captured Confederate General Rosser after a battle and hugged him, because they had been close friends at the Academy. Before the Rebellion, Union General Hancock and a Confederate General opposed to him at Picket's Charge were close friends.
Future Union General George Crook and future Confederate General John Bell Hood were close friends in Oregon before the Rebellion.
Union General Phillip St. George Cooke (not the Confederate General Philip St. George Cocke) was the father in-law of Confederate General J.E.B. Stuart.
And so on and so on. Many examples.