As the reading of the will begins, there is a briefcase, an ashtray, and a desk pen holder (and pen) on the table. After describing all the traits of the favored dog, the desk pen holder and ashtray have disappeared. Also, several loose papers have appeared, but should not be there, as the will is bound in a blue folder, and the pages would not be loose that way.
When Spike covers Droopy in foamy shaving cream, he does so from Droopy's left side, and the chair Droopy is dozing in has nothing but a wall next to it on that side However, when the dog catcher arrives minutes later, on Droopy's left there is an end table with a book and a running electrical fan on it.
As Spike's jaw drops to the floor when Droopy is announced as the sole inheritor, it breaks a large hole in the wooden table. The table hole has many jagged edges, but the wood pieces on the floor are mostly rounded (like "punch-outs" on a modern desk to allow electrical and computer cords to pass through).
When Spike is portraying himself as "clean-minded", puts his hands (front paws) over the "bathing beauty" on a 1949 calendar. The month shown is January, with New Year's Day being Monday (or maybe Sunday). In 1949, the year began on a Saturday.
The last paragraph of the will states, "However in the event of Droopy's death, the entire estate shall revert to Spike." The use of "revert" is incorrect; that would mean that Spike was the owner of the estate before Droopy. A better term would have been "be conferred".
When Spike sets up the gas explosion, if the mixture of gas and oxygen were enough to explode in the manner shown, the spark from the lighter would have been enough to initiate the explosion - a flame from the lighter would not have been necessary. Thus the warning that, if you smell gas, do not plug anything in or flip any electrical switches, as any electrical spark created by these actions would be enough to cause an explosion.
When Spike sets up the camera to take Droopy's picture, and it backfires, Spike's head (when visible from the front) is covered with a black cloth. When he turns and is seen from the back, there is a hole in his head. If the hole was not visible from the front, it should not have been visible from the back either, because of the black cloth.
When the lawyer reads the will, at the end, he states that, upon Droopy's death, "... this entire estate ...", whereas when the will is seen, it reads, "... the entire estate".