As Martin sings "Skip to My Lou" while skipping down the hallway, he says, "Top of the morning" to Nelson, who replies, "And to you too." This is moments before the bake sale, which is clearly at 3 o'clock in the afternoon.
Lisa sends Bart about six pictures of Jimbo's house as schematics after claiming that there are only a couple of pictures. However, the definition of a "couple" is "an indefinite small number", therefore, six could be a valid number in relation to Lisa's use of the word "couple".