The monitor above Hal's lane at the bowling alley reads Lane 15. However, the number above the pins indicates he is actually bowling at Lane 26.
When malcolm gets mad and starts walking towards the pins he gets two steps onto the lane but in the next scene he is not even on the lane yet.
Early in the story and before the first commercial break, when they go to split screen showing the different realities of Lois vs. Hal taking the boys bowling, the version where Lois takes them is on the left and the version where Hal takes them is on the right. But in the closing scene, where they return home, the Hal version is on the left and the Lois version on the right.
Hal goes to read "Wilbur the Worried Worm" to Dewey but when he sits down to read it, you can clearly see Princess Atta (Disney's "A Bug's Life" 1998) on the inside of the book.
At the bowling alley, Lois asks for two pairs of shoes, size 9 and size 7. The man walks off to grab them. She needs several seconds to realize she doesn't have enough money and changes her mind, asking the man for a single pair of size 8's. He is already handing her the single pair before she can finish asking.
In Hal's final, crucial game when Malcolm's clothing gets caught up in the machinery, Hal bowls a gutter ball to his right.
Near the end of the episode, when the bowling patrons leave Hal's quest for a perfect game in disappointment, a camera and a camera operator are visible in the bottom right of the shot.