When Major Winchester is transferred to the 4077th by Colonel Baldwin, he is a full-bird Colonel. However, when Colonel Baldwin visits the 4077th he is a Lt. Colonel.
When Charles and Horace Baldwin are playing cribbage in The Swamp, Charles says that Baldwin has erased his debt of $623. However, when Baldwin hands Winchester over to Potter in Fade In, Fade Out, the debt is $672.17 (after his initial error of $672.13).
When procuring the Korean prostitute in Rosie's Bar, Charles tells her to call on "the MASH VIP at 11:30." But the prostitute would not be able to enter the camp on her own. Like any military post, the 4077th has sentries to prevent non-military personnel (or enemy personnel) from accessing the camp on their own.
While counting up Hawkeye's jokes in the OC, BJ misses counting "No Horace-ing around"