There are two Great Northern services originating at Kings Cross which cover all or some the Thameslink semi-fast outer suburban stopping pattern but then continue from Cambridge all stations to Kings Lynn.
06:01 1T94 KGX-KLN arrives 08:03, calls Finsbury Park, Stevenage, Letchworth, Baldock, Ashwell & Morden, Royston, Cambridge and all stations to KLN
23:17 1T72 KGX-KLN arrives 01:14, calls Letchworth, Baldock, Ashwell & Morden, Royston, Cambridge and all stations to KLN.
The first one replicates Thameslink calls, and is half an hour before the first through service from the core up to Cambridge.
The second replicates some Thameslink calls, at a time when Thameslink to Cambridge drops to hourly and then ceases.
In the other direction, only one, the last KLN starter also effectively fills in for Thameslink after the last through service has gone.
22:49 1T97 KLN-KGX arrives 01:04, calls all stations to Cambridge and then the Thameslink semi-fast calling pattern but terminating at Kings Cross.
There must be loads like this at the extremities of the day where service thins and first/last calls must be made.
...
The other example I have in mind are the two EMR Nottingham to Norwich services that identify as CrossCountry services:
04:56 1L01 NOT-NRW calling at Loughborough, then Melton Mowbray, Oakham and Stamford, and then normal routing from Peterborough
06:07 1L02 NOT-NRW additionally calling at East Midlands Parkway
There are no equivalent oddities westbound; the first XC leaves Peterborough at 06:07 and Leicester at 07:05.