Goof: When Pim throws the sack of money into the capsule thinking it will go to the future with her, she is wrong. It would only make it to the future if it remained in its spot. Naturally someone would take it out of the capsule some time after that. The note would go to the future unnoticed because no one has any reason to remove it from the capsule. Also the paradox of Pim never existing in the past, and never raising the money in the first place also explains the fact of the money never making it to the future.
Goof: Lloyd says that he found the capsule on one of his and Barbara's famous picnic dates. Although in the flash back at the end of the episode he says that they are going to rent a time machine. Why would they do this if Phil and Pim weren't born yet?
Goof: Scientifically, if something is engraved (or in this case, printed) on a tree near its trunk, especially at the base, it will stay the same height above ground, no matter how tall the tree grows, even in one century.
In a hundred years, H.G. Wells Jr/Sr High School was torn down and replaced with a park, when this change occured is unknown.
Goof: Did the family rent or buy the time machine? According to the theme song and the promos that preceded the premiere of the show, the family rented a time machine. But according to this episode, Lloyd bought the time machine from a store that sold used time machines (and water slides) while he and Barbara were dating. So which was it?
Although they are stuck in the past, according to the end of this episode Barbara and Lloyd were both originally from a future Pickford.
Goof: When the flashback is shown of Lloyd and Barb's picnic, it was supposed to be taking place when they first started dating. However, they are both wearing wedding bands in these flashbacks.
If the note were read and the advice followed, it would've created a time paradox. The Diffy's wouldn't have gone to the past; thus, the note wouldn't have been written. If the note weren't written, things would be how they are, with the Diffy's in the past, writing the note.
Pim: Start forkin' over the green stuff! The higher the domination, the sooner this bell stops ringing!
Phil: I thought being remembered a hundred years from now wasn't important. But I'd give a hundred years of memories just to remember the most important, special, wonderful person I've ever met...Keely Teslow.
Apparently Pim is still Science Club President from when in Versa Day, when Phil in Pim's body made her become the president.
Keely: (sing-songy) Twenty-first Century Phil!
When Keely says this, she does so in a sing-songy way, similar to the show's theme song/lyrics. However, she replaces "22nd Century Man" with "21st Century Phil."
Time Release Capsule is a play off of a medical term usually used for aspirin capsules.