Don't forget that a parenthetical has to be surrounded by punctuation. When the parenthetical follows the word and, for example, there has to be a pair of commas around the parenthetical.
...And in the morning we noticed the crack. (a prepositional phrase that is NOT a parenthetical but is just a modifier)
...And, by the way, we noticed the crack. (a prepositional phrase that is a parenthetical)
...And by 10:00 he was ready to go. (a prepositional phrase that is NOT a parenthetical but is just a modifier)
...And, at any rate, he was ready to go. (a prepositional phrase that is a parenthetical)
Happy punctuating!
Margie