Ah yes from a long time ago. If you _really_ want some fun in your scheme code. Add something like the following to your .emacs file as a scheme-mode hook. Essentially all standard scheme "keywords" / special forms are reduced to _display_ as single char greek letters. What is sort of cool is the source code stays unmodified and works just fine. Emacs only displays the string "lambda" as a λ etc.
This was done as sort of joke years ago so the matching regexs for the compose-regions are pretty naive. The lambda thing added to quack and later racket added it as well. I originally found the lambda thing by accident after I saw someone else using "compose-region" for some similar purpose. Can't recall. Stephan Monnier?
;; Pretty Lambda and delta character
(defconst schemecmpct-lambda-char (decode-char 'ucs #x03BB)) ;; (make-char 'greek-iso8859-7 107))
(defconst schemecmpct-delta-char (decode-char 'ucs #x03B4)) ;; (make-char 'greek-iso8859-7 100))
(defconst schemecmpct-beta-char (decode-char 'ucs #x03B2)) ;; 'greek-iso8859-7 98))
(defconst schemecmpct-rho-char (decode-char 'ucs #x03C1))
(defconst schemecmpct-sigma-char (decode-char 'ucs #x03C2))
(defconst schemecmpct-iota-char (decode-char 'ucs #x03B9))
(defconst schemecmpct-log-and-char (decode-char 'ucs #x2227))
(defconst schemecmpct-log-or-char (decode-char 'ucs #x2228))
(defconst schemecmpct-log-not-char (decode-char 'ucs #x00AC))
(defconst schemecmpct-log-true-char (decode-char 'ucs #x22A4))
(defconst schemecmpct-log-false-char (decode-char 'ucs #x22A5))
(defconst schemecmpct-less-equal-char (decode-char 'ucs #x2264))
(defconst schemecmpct-greater-equal-char (decode-char 'ucs #x2265))
(defconst schemecmpct-key-words
'(("[[(]\\(case-\\|match-\\|opt-\\)?\\(lambda\\)\\>"
2
(progn (compose-region (match-beginning 2)
(match-end 2)
schemecmpct-lambda-char)
nil))
("[[(]\\(define\\)\\(-.+\\)?\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-delta-char)
nil))
("[[(]\\(let\\)\\(*\\|-\\)?"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-beta-char)
nil))
("[[(]\\(set!\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-sigma-char)
nil))
("[[(]\\(begin\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-rho-char)
nil))
("[[(]\\(if\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-iota-char)
nil))
("[[(]\\(and\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-log-and-char)
nil))
("[[(]\\(or\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-log-or-char)
nil))
("[[(]\\(not\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-log-not-char)
nil))
("[[(]\\(<=\\)"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-less-equal-char)
nil))
("[[(]\\(>=\\)"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-greater-equal-char)
nil))
("\\(#t\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-log-true-char)
nil))
("\\(#f\\)\\>"
1
(progn (compose-region (match-beginning 1)
(match-end 1)
schemecmpct-log-false-char)
nil))
("[][()]" . 'schemecmpct-paren-face)
("#[\\]\\w+" . 'schemecmpct-character-face) ;; characters
("#x\\w+" . 'schemecmpct-character-face) ;; hex numbers
("\\w+set!" . 'schemecmpct-dangerous-face)
("\\w+!" . 'schemecmpct-dangerous-face)
"library" "import" "export" "provide" "require" "not" "#t" "#f" "aif" "define-record-type" "struct"))
(defun schemecmpct-install-fontification ()
"Install font lock extendsions to scheme mode."
(font-lock-add-keywords nil schemecmpct-key-words))