In #45 "Sales Resitance" Lucy says that her Handy Dandy Kitchen Helper cost $7.98, but later in that episode she says it cost $7.95. (thanks to Kayla's 'I Love Lucy' Page)
Episode #98, "Lucy Cries Wolf", has Lucy going out on the ledge so that Ricky will think she's disappeared. The ledge runs parallel to the Ricardo's living room wall and ends in the corner. In episode #166, "Lucy and Superman", the ledge outside the same window now runs around the corner to the vacant apartment next door. Additionally, there's now a drainpipe in the corner. (Thanks to Charlie Anderson)