I Like This One!
It's been a while since I've seen the others, however many there may be, and This network keeps reshowing this one, but I get a kick out of this one.
From the corny laughter bit with the 'big-wigs' laughing at nerd for wanting to build his airship, to the chauffer, Parker, the opening theme; the cheesy way the bad guys recorded things Penelope said to form a message (that didn't work); Penelope herself!
Cliff Richards cameo, what more could you want?
I'd like to see the other ones sometime, mainly just to see what they are like, but I really enjoy this one.