One of the many sporting figures to be lampooned by the Daily Mail cartoonist Thomas Webster was the racehorse Tishy. As Webster's obituary in the 22 June 1962 edition of the Times put it, "It was he who made a national joke of the famous racehorse Tishy, which was reputed to cross its forelegs when running."
Webster's Tishy cartoons for the Daily Mail can be sampled here. He must have been very fond of the horse, as he was still drawing her as late as 1939 - even though, as acknowledged by this 1931 cartoon, the real-life Tishy was no longer among the living by that time.
In 1922 Tishy made her debut as an animated character (an event that Webster commemorated with this cartoon) in a film titled simply Tishy - although Giannalberto Bendazzi's Cartoons gives the film's name as Tishy the X-Legged Horse, a title that I have not found in any other reputable source. It was reviewed in Bioscope 1 February 1923 (a review that was later quoted in Denis Gifford's British Animated Films, 1895-1985: A Filmography):
The subject of the film is the now famous racehorse, Tishy, who is shown plaiting her legs in readiness for the start, and then advising the jockey to get off and take a taxi. Although the rest of the field has long since passed the winning post, Tishy continues her shambling way, while the crowd waits patiently for her arrival. Night falls, and the moon climbs high into the sky, before she completes the course and drops, a shapeless mass of twisted limbs, at the post. Thanks to Mr. Webster's brilliant draughtsmanship and inimitable captions, the film is even finer than the original cartoonsGifford says that the short was given a royal premiere at the London Hippodrome on 12 December 1922. The animated Tishy cartoon can be viewed on the British Pathé website - it's part of a longer video, however, so you'll have to skip forward to around 10:30 to see the cartoon.
Most of the sources I have seen that mention the film credit Webster as the director; however, the opening credits of the film identify it as being directed by Tom Aitken "under the personal supervision of Tom Webster". Gifford's book lists Webster as director, producer and writer, Aitken as camera operator and W.D. Ford and Joe Noble as animators. The only copy of the film I have access to right now is the one on the British Pathé site, which lacks any credits besides those of Webster and Aitken.
Was this all of Tishy's career as an animated star? Not according to the BFI database, which identifies Tishy not as a short film but a whole series. Outside of that page, however, I have found no evidence that Tishy ever starred in any further animated cartoons.