The picnic was supposed to occupy the second reel, but the gags in the preparation and departure got so involved that they filled the entire two reels.
The bungalow in front of which much of the movie was filmed was/is located on Vera Avenue in Culver City, and belonged to Baldwin Cooke, the actor who plays the Boys' next-door neighbor in the film.
In preparing to leave for the picnic, a large cylinder gets knocked off the table. Oliver picks it up and listens to it as he shakes it. The item is a Thermos jug for keeping liquids hot or cold. The original Thermos had a metal exterior and a glass interior, so if the jug was severely jarred or dropped the glass interior could break thereby rendering it useless. Oliver was listening for the rattling of glass shards to indicate the jug was broken.
Perfect Day is the only Laurel and Hardy work that features profanity. This happens when Edgar Kennedy says "Oh, shit!" (at 12:19 into the 19 minute running time), whilst the family rushes back into the house when they see the local parson coming down the street.
The version presently available is a late 1930's re-release with background music from the Block-Heads period added throughout. It's also been visually converted from its original taller, narrower 1.20:1 early sound ratio to the 1.33:1 standard ratio, so that tops of heads get chopped off in several sequences.