A Hitch in Time [1978]

The lowdown: 'A Hitch in Time' was produced for the Children's Film Foundation, which specialised in producing low-budget
films aimed at a young audience. It stars Patrick Troughton as a scientist, Professor Adam Wagstaff (who may or may not be
a mad scientist, and claims to have invented a time machine. Two children on their way to school here strange noises coming
from an old castle, and find Professor Wagstaff trapped within part of his machine. The two kids rescue him from the clam-like
device and he explains that his time machine is called OSKA ('Oscillating Shortwave Kinetic Amplifier' - apparently the name
TARDIS was taken). OSKA works, Wagstaff assures the kids, the only problem being that he weighs too much for the system
to transport through time. But weight... I mean, wait... the two kids' combined weight can easily be handled by OSKA.

Wagstaff tries sending the kids back in time three months, or so he thinks. But the machine blows up and he thinks it has not
worked. The kids go off to afternoon classes at school, and find that it is that morning again. The machine works! Yihoo! says
Wagstaff. Time to send the kids further back in time. They dress in Robin Hood-era clothing and Wagstaff sends them back to
1190, but of course OSKA blows another fuse and they end up in 1953, on the day of the coronation. They embark on a series
of trips through time, and end up in 1816, the Civil War of 1645 and the Stone Age. In each trip back in time they encounter an
ancestor of their schoolteacher, 'Sniffy' Kemp. Wagstaff eventually gets OSKA properly tuned so it will carry his weight, and he
embarks on his own trip through time; dressing as a court jester he travels back to medieval times when his castle was brand
new, but discovers that his corny jokes are as funny in 1364 as they are in 1978.